London and a day trip to Paris too much with an 11 year old in 4.5 days?

If Paris is really on the top of his list, it is certainly possible to do a day trip and spend a few hours in Paris. In that case, buy the train tickets as soon as possible as they can get expensive. And remember there is a one hour time difference between the cities.

Probably too late -- how about flying into London and coming home from Paris? You could do it, but it will be a long and trying day. One extra wrinkle is that you have to go through immigration and customs at both ends so that puts a couple extra hours on the travel time.

Ahh, hadn't factored in immigration/customs properly. Does anyone have a rough estimate of how long customs may take between France and the UK? My last train trip between countries was Czech Republic and Germany, and I don't remember it being especially long.
Yes, plane tickets already booked. It was much higher flying into or out of Paris, but given how much he wants to go I'm trying to add it in this way.

I just looked at a date in April, a round trip ticket to Paris would be $159.00 for each person.

Germany and the Czech Republic are both Schengen countries. The UK has never been a part of Schengen, and is now no longer part of the EU. Eurostar recommends that you arrive 90 minutes before departure for immigration and customs.

Thank you, I'd forgotten about that!

Be sure you are being honest (and realistic) about how you are counting your usable "days." Personally, I find that when I start talking about what I hope to accomplish in "half days" (or less), it's a usually a sign that I'm being unrealistic with myself about how much I can actually get done (because I'm trying to squeeze in too much): "I'll have one-and-a-half days here, half a day there there." When I catch myself slicing days into fractions, I usually need to sober up and take an honest look at my plan.

Is that "half day" you are counting your arrival day after a trans-Atlantic flight? If so, I would be careful about your expectations for that day. For me, I don't think it's realistic to count any portion of my arrival day or my departure day as usable (regardless of the flight schedules). And of course any time you pick up and move to a new location, that consumes from 1/2 a day (best case) to most of a day. When I've planned fractional days, that usually means I won't get much value out of that (partial) day.

Flying in to London and out from Paris would save you a portion of a day by avoiding backtracking (OTOH it changes an out-and-back day trip into a relocation day, which involves hauling luggage, finding your way around in a new place, and checking into a hotel, etc., all of which will slow you down).

I think you are shortchanging both London and Paris to try and do this in a 4.5 day stay.

Say you are up for an early start to maximize your time in Paris. You take the 7:01 outbound to Paris. You would have to be at St. Pancras by 6:00 AM. You arrive Gare du Nord at 10:23. (There is a one hour time change.) You’ll take a taxi or the Metro to somewhere central, your first site.

Assuming you’ll run out of steam after 12 hour or so, you plan on the 19:13 EuroStar return, meaning you have to be at Gare du Nord at about 18:00.

This gives you 7.5 hours in Paris. Check the prices, but depending on how far in advance you buy it will be about $400 for just your EuroStar fares. Check schedules and prices here https://www.eurostar.com/us-en.

Is it worth it? Maybe next time you go to Europe?

I missed Badger’s comment about the 90 minutes in advance. I forgot about that as I haven’t take the EuroStar since Brexit was finalized. Ugly and time consuming wrinkle.

I appreciate all of your comments and it really is too much of a stretch in such a short time, especially with the extra time I hadn't properly considered through customs each way.

One more question; has anyone done Easyjet? The flights are very affordable, though it's a similar time consideration getting into and out of the airports.

EasyJet is one of the most popular airlines in Europe. They are a "low cost carrier" (LCC) so you need to clearly understand the requirements (and follow them to a "T") but for an LCC flight, they're fine.

Whilst EasyJet are a fine airline, if you're thinking of flying to Paris rather than taking Eurostar then frankly forget it. It will take at least an hour to get out to the airport (probably Gatwick), you need to arrive two hours before the flight and then you have to get into Paris from CDG. And then repeat on the way back.

EasyJet is great. That is our preferred discount airline. Reminds me of SW in the states. But that is not a solution for your situation. You have same issue. Since G Britian is not a part of the Schengen zone you have to go through immigration/customs when entering and leaving France.

Flying will probably take you 5 hours each way, maybe longer depending on your starting point. That’s an hour longer than the train. And on the train you sit down in the centre of London and get off in the centre of Paris. Flying you need a train at each end as well as the flight coupled with the hassle of transiting two large airports twice in a day.

If your 11 year old wants to see Paris, I would go see Paris. This can be done in a day trip, however, I recommend doing it as an overnight. You lose out on a full day of London but pick up a full day in Paris. Too bad you only have 4 1/2 days.

I missed Badger’s comment about the 90 minutes in advance. I forgot
about that as I haven’t take the EuroStar since Brexit was finalized.
Ugly and time consuming wrinkle.

Although 90 minutes is what they recommend, you can probably do it in less. Although with non-EU passports you do want a bit of time to spare.

I appreciate all of your comments and it really is too much of a
stretch in such a short time, especially with the extra time I hadn't
properly considered through customs each way.

It's not what I would recommend, but it can certainly be done if seeing Paris is important. If you get to Paris 10:23 (remember, no checks on arrival and the train arrives in central Paris.) you certainly have time to see a bit of Paris. The last train back to London leaves 21:13, arriving 22:30 (now the time difference works in your favour), and you should probably be back at Gare du Nord around 19:45. That is nine hours in Paris after all.

One more question; has anyone done Easyjet? The flights are very
affordable, though it's a similar time consideration getting into and
out of the airports.

If you're doing Paris as a day trip you want the fastest option, which is the train.

it sounds so easy to do the Chunnel but if you do any research into the current state of Eurostar, it's frankly a mess. Brexit really messed with the ease of use and trains are leaving mostly empty. And as noted, flying also looks quick and cheap but you have to get from one city center to another.

you really need to focus on either city, sorry.

A different view: he is 11 years old, and has lots of time ahead of him to see Paris. Why does he want to go? What does he want to see? And what does he actually know about Paris? Has he studied French? Read a book that created fantasies about Paris?

A daytrip there would be a very expensive, time-consuming, and tiring way to satisfy his wish, and may not not satisfy him at all. He has no idea of the time and trouble involved—especially the long time of waiting in lines at St. Pancras (done that, yuk) and then more of that on the way back. It isn’t like you can just rock up and get on the train in either place. As a parent myself, I can testify to the dangers of creating unrealistic expectations in children. A total meltdown from disappointment is not a pretty sight.

You appear to be an experienced traveler and have actually taken him to Europe before (Switzerland when he was much younger.)

https://community.ricksteves.com/travel-forum/switzerland/multigenerational-trip-to-switzerland-in-july-suggestions

Give him a reality check on the time and hassle involved for Paris, and let him know you feel it would be much better to leave Paris for a later time, when you can spend more time there. And then show him all the great things you can do in London. Is he interested in Harry Potter at all?

Depending on your plan for Paris, maybe take the last flight of the evening to Paris Orly from London. Get into a central hotel in Paris, late and get 6 hours of sleep and get up and start your day. Then take a late flight back to London or the train. Just a thought. I’m not sure if they offer sleeper trains from London to Paris. I say do it! Everyone always says each city deserves this much time. But in reality some people don’t have that time. I would rather get a glimpse of it than not see it all. Probably wouldn’t do any museums or pick one and only see the highlights of what you or kiddo wants to see.

there are no sleeper trains on that 2 hour route.

I would do the overnight to Paris. This is your son's trip too and he will enjoy it more if his wishes are accommodated. I would consider flying to Paris when you arrive in London and spending at least one night in Paris. This will avoid splitting up you hotel nights in London, since you will need to be in London the night before your return flight.

It's probably too late to comment on this thread now - you may already have made your plans. However, I want to say that I did this with my 18-year old son last month. We took the 7:01 Eurostar to Paris and the 21:03 back to London. We took the tube to St. Pancras and got there about 5:45am and there were very few passengers there; other passengers started coming in after 6am. The main thing I was afraid of was strikes in either UK or France, but we got lucky. Immigration at St. Pancras took about 10-15 mins and at Gare du Nord about 20-25 mins. Both stations are located in the center of the cities, so very easy to get to both ways. The only suggestion I have is to confirm the timing and station to use for the early morning tube in London. The day trip was totally worth it for my son, who especially asked for this mother-son trip as his 18th birthday present. We had enough time for the Orsay, walking about for some street photography & crepes at the Jardin des Tuileries and seeing the Eiffel tower as the lights came on, and the twinkling lights at 7pm.

Sorry, but an overnight day trip to Paris is a bad idea for anyone. Go to Paris when you can spend several days to take in the city, not just a windshield tour.