Should we go to England?

I'd always vote for London :)
The only vote that matters is your son's :)
I've heard there are cheap flights from Ireland to London, my brother in law who lives in Essex just did it a couple of weeks ago, to go see a concert in Ireland. He's seeing great prices on flights, he said.
So much so that they're coming here to visit my daughter (his niece) next month in NH.
Have a great time!

Tempting as it may be, with no female supervision and all, to spend those couple of days in England, I'd recommend staying in Ireland because of the time it will take to ferry or fly to England and then make your way to (presumably) Heathrow. Unless you decide you dislike Ireland, you'll probably want to spend more time there. Many things to occupy unsupervised males in Ireland, I'm told. Pubs come to mind.

BUT, you might find a really cheap fare home from London, or perhaps Manchester, that justifies the England weekend. Or your "who knows what" might become something specific that you really want to see or do in England (and can't do in Ireland). Pubs don't count -- both countries have them and you won't have time to explore fully the differences and comparative advantages.

And I agree that your son's vote should count for more than yours. With all due respect, dad. ;-)

I just ran it by the Boy. We have been to Ireland twice before. He says "Can you maybe check for a cheap flight from Dublin to Scotland? I'd really like to see a bit of Scotland. Then we can train to London (we were in London four years ago) and fly home from there.

I'm booking mileage flights so the cost to fly home from London is the same as from Dublin in miles.

Sheesh,

A train from Scotland to London could be very expensive.

with such a short time -- travel Friday, time there Sat and Sun, and then fly home Monday, I wouldn't go to the trouble of going to another country, I'd stay in Ireland. (Especially if you've been that many other places in the previous two weeks.)

(Not to mention if you go to Scotland, it's: travel Friday to Scotland, have Sat there, travel Sunday to London, fly home Monday.)

That's an awful lot of churn not to see very much.

Since you are in the early stages of planning, I would suggest not taking a train to London just to fly back homewards. Fly direct from Edinburgh or Glasgow if you can, otherwise connect in Dublin.

As half your family is leaving Friday and you are departing Monday, that only really leaves you 2 days somewhere. A 2 week holiday including Prague, Paris and 5 days in Ireland is a hectic schedule so I would seek some relaxation for your 2 days.

Flying to Scotland then taking a train to London is going to eat further into your limited time. P and O are the only ferry operator offering the Dublin-Liverpool route, which takes 8.5 hours and doesn’t appear to be available for foot passengers. Either fly home from Scotland or stay in Ireland would be my preference.

I suggest planning a future trip to England where you spend more time there. Also, don't forget Wales, it is beautiful.

Nothing wrong with Liverpool, unless you are obsessed with Beatles trivia.

We did a four week drive tour of Wales and England and loved it. Here is my detailed review:
https://www.cruisecritic.com/memberreviews/memberreview.cfm?EntryID=599139

You have only two extra actual days of sightseeing, not counting Friday (a transit day if you leave Ireland) or Monday (consumed with getting to the airport for your flight home). So, I'd either stay in Ireland, or use Emma's suggestion of flying from Dublin to a place in Great Britain for 2 days, as long as you can then fly home from that place. If the departure airport is London, figure out how you will get to London the day before your flight home, and remember to subtract that travel time from your sightseeing time.

There are nonstop flights to some North American cities from Glasgow, Edinburgh, and Manchester. Or, you can connect through Dublin from almost anywhere in the UK.

If you can fly home from Glasgow or Manchester, you may find some ideas of how to spend time in Glasgow, Manchester, or Liverpool from my trip report. All three of them have lots to see and do, and Liverpool has plenty of non-Beatles sights too. All three are also very different from London, and as a bonus, much cheaper. https://community.ricksteves.com/travel-forum/trip-reports/uk-trip-report-glasgow-manchester-liverpool-in-september-2016

I'd go to London-we found it more difficult to get a flight going to Edinburgh(using frequent flier miles) and traveling from Edinburgh to London would be a big waste of limited time. We flew to Edinburgh this summer using frequent flier miles and went through 5 airports, counting Edinburgh-It took us 2 days! (although I made a poor decision that resulted in one more airport than was really necessary and we had to go thru NY instead of Atlanta to get business class going over the pond-so you won't feel too sorry for us!) We like London so much that we have been known to schedule an overnight (or even an entire day and put our luggage in storage until an evening flight elsewhere) there on our way back to the US from another country (with frequent flyer miles, it's easier to find fights back to the US from London and if we're going to connect in Europe anyway, it might as well be London) If you leave early Friday morning from Dublin, you would have 2 1/2 days in London. Tthere will be lots of hours of daylight in summer and I think some museums are open Friday night during the summer.

Western England, and Wales have a lot of attractive places, although maybe easier with a car. I don't find post-industrial cities anywhere to be that enthralling, but if you are interested in the track of the Beatles, or something like that? How about the Lake District? Half joking, the Wall Street Journal mentioned a special (decorative arts?) museum somewhere up there where there is a clockwork swan the WSJ called "A Masterpiece".

The Silver Swan, but that's in Barnard Castle, not in the Lake District.

Listening to Marco and others, I have booked our return home flight from Edinburgh non-stop to O'Hare. I will get the flight from Dublin to Edinburgh later.

While I know this is hectic, I am 71 years old, and although fine now, have had serious health issues. I do not know if I will get back. A chance to spend a few days in a very cool place with my son whom is also my friend is a treasure I cannot pass up.

C'est un fait complete!!!

Well Joseph now that does sound nice. Glad you have made your decision and found a good flight home. Edinburgh is a wonderful city, and I hope you and your son enjoy your time together there very much!

joseph, sounds like a very good plan to me. I hear you about spending time with your son and friend, in a new, cool place... priceless. Have a great time!

Excellent plan, now enjoy your unsupervised time together!