London on a Sunday afternoon

Assuming they will get Oyster cards for transit around London, they could hop on a regular Transport for London (TfL) red bus for a ride. Here's an article about the best routes for sightseeing: https://www.tripsavvy.com/london-bus-routes-for-sightseeing-1582177

I'm familiar with the Number 24 route which is mentioned in the article. There won't be narration of course, but if it's a nice day and they can snag seats upstairs on the bus it could give them an overview of some of the sites they may be visiting later on their trip.

Also, Transport for London's website has a page about leisure bus routes which I've found helpful: https://tfl.gov.uk/travel-information/visiting-london/experience-london/bus-leisure-routes

London has some nice parks. I'm most familiar with Hyde Park which isn't right next to Victoria but is linked by bus routes, like the Number 148. Of course there's also the Tube. Again, if the weather's OK just strolling around in a park would be pleasant.

For me, staying outside in fresh air is the best way to fight the jet lag on arrival. If they arrive at 10:00, it will be at least noon by the time they check into their lodgings.

After a quick lunch I'd suggest what has become a first day tradition for us- taking Rick's self guided Westminster walk up to Trafalger Square followed by tea and a snack in the crypt at St Martin in the Fields. Usually we then go to the National Gallery for a couple of hours; but in this case they could walk some more, going up the Mall to Buckingham Palace before returning to their hotel.

It is so nice of you to help plan your son-in-law’s and grandson’s first trip to London. Staying outdoors is wise to combat jet lag. Here are some other suggestions, especially if they can’t sleep on the plane.

• If they are flying business class, I would recommend the airline’s arrival lounge. Getting a shower and freshing up after a long trip, can be rejuvenating. If they are not flying business class, check with their B&B on a potential of early check-in that way they can take a shower and rest if needed before hitting out for the day.
• If they can’t check in early, then I would drop luggage off at a B&B and head out for brunch/light lunch and explore the areas you suggested. Here is a list of the top things to do in London on a Sunday: https://www.tripsavvy.com/free-sundays-in-london-1582884.
• Join a walking tour: http://www.walks.com/our-walks/sunday-walks. London Walks have great tours (including one on Sunday’s for Harry Potter locations). It is relatively inexpensive and having a guide takes the burden off your son-in-law to navigate if they are tired. If it is too much, because it is so inexpensive, they can leave the tour at any time and not feel guilty about wasting too much money.

Hope they have a great trip,
Sandy

Assuming it is a nice day, getting out for a walk is the best thing to do on arrival day. Your suggested plan is a good start.

With a 10:30 arrival, it will be after noon by the time they get through immigration and travel into London. If they are ready for lunch, they could drop their bags at the B and B and find a spot right close by. There is a Pret a Manger in Victoria Station, along with other options, but your grandson might really like the Shake Shack whichnis across the road from Victoria Coach Station. Or if they can wait to eat, they could make their way to the London Eye area and choose on of the casual cafes strung out along the pedestrian path heading north from the Eye. Giraffe would be a good choice.

after lunch and a ride on the London Eye, they could walk a bit South along the river for the best view of Parliament. Note that the Elizabeth Tower ( aka Big Ben, which is the clock bell itself) is covered up for renovation, so you won't see that.

Then turn and walk North again on the path for a bit. There is a much-used skate parkmalong there and the boy might enjoy watching the action. There is also an outdoor book sale and flea market, but I cannot remember if it operates on Sundays. Lots to see there if they want to keep walking, such as the Globe Theatre, St. Paul's acrosss the river, buskers, replica of the Golden Hinde, HMS Belfast (battleship) and more. If they get as far as Tower Bridge they can cross to the Tower of London area and take the #15 bus to Trafalgar Square, and either walk or take another bus back to their B and B.

Bus map:

http://content.tfl.gov.uk/bus-route-maps/key-bus-routes-in-central-london.pdf

If that sounds like too much, they could cross on the pedestrian side of the Hungerford Bridge ( the first bridge north of the London Eye) and end up at Trafalgar Square on foot. Then walk down the Mall to Buckingham Palace, stroll through St. Ja,Es Park, and back to the B and B from there.

Since they are arriving on a Sunday, and the trip is more than 90 days away, I am going to suggest an easy and fun way to,get from Heathrow to Ebury Street. The normally expensive Heathrow Express train will cost them a total of £5.50 if they purchase the ticket 90+ days in advance ( so in Early December). That is the adult fare for weekend travel, and the child is free.

https://www.heathrowexpress.com/tickets-deals/prices-fares

The train is fast ( 15 minutes into London Paddington Station) and comfortable. Note that the HEX serves T2, T3 and T5 at Heathrow, but not T4. If their flight comes in there, they would be better off with the new TFL service, formerly known as the Heathrow Connect. Oyster cards will work on that train. Either way they will arrive at Paddington ( is your grandson familiar with the Paddington Bear stories?). They can then catch a black cab from the stand just outside the station for an iconic London experience, and a chance to sightsee a bit and get their bearings on the way to Ebury Street.

We have enjoyed Greenwich on a Sunday. After checking in at their b&b, they could grab a quick lunch, then take boat (from near the London Eye/Parliament) or the Tube up to Greenwich. When we visited, there was a nice market to stroll through and then we headed to the park. Lovely place to stroll, sit and rest and watch all the dogs frolic. And there are all the nautical 'stuff' to see and do , if they want. As they leave they could grab items for supper from some of the stalls.

I usually stay at The Lime Tree hotel on Ebury St. My go-to walk is to walk toward Buckingham Palace on Ebury, then walk alongside the back wall of the palace to Hyde Park corner/Wellington Arch. See the war memorials in this area, then cross the street and see the RAF Bomber Command Memorial. Work your way back to the front side of Buckingham Palace, then thru St James's Park to see the various waterfowl on the small lakes there if the weather is holding. I'd head back along Birdcage Walk toward Buckingham Palace Road, then back to their lodging.

I agree with the post above on the time frame for getting to the hotel as being after noon. I'd eat first as well then head out. There is a very good gelato shop near the corner of Elizabeth Street and Ebury Street!

Which lodging are they staying in? If it is toward the Elizabeth Street part of Ebury Street it is WAY easier to take the National Express Coach to Victoria Coach station from Heathrow. I realize you didn't ask this but thought I would throw it in.

Easy answer.

Once they’ve checked in to their B&B to freshen up they can walk towards Victoria Station and Dad should look for a bank ATM to get their pounds. From there to the train station to purchase their Oyster cards if they haven’t already bought them at Heathrow.

Imagine the 11 year old would find riding the Underground fascinating and for that matter seeing a train station as large as Victoria would probably be an eye opener.

They’d need to board a Circle or District line train to the Westminster station, Mind The Gap, exit the train and exit the station. I suggest the exit that says Westminster Bridge. Takes you out to the Thames and where they’d see the Eye across the river. If they turn right and look up they’d see Elizabeth’s Tower. Unfortunately it will be under scaffolding. Climb the stairs and walk across Westminster Bridge to Jubilee Gardens and ride the Eye.

From there cross back over Westminster Bridge to Parliament Square and turn right and walkup Whitehall to the Horseguards. From there up to Trafalgar Square. The 11 year can try to climb the lions.

Easy jaunt via the tube back to Victoria. Charing Cross via Northern Line to Embankment then a District or Circle Line train. By this time they’ll be London Underground pros.

EDIT: Before leaving the B&B they should ask their hosts where they could enjoy a Sunday roast. If close by they should stop in to make certain they didn’t need reservations for that evening or make them. Then make their way to Westminster and Parliament Square.

Thank you all for your terrific suggestions. The Harry Potter London Walk would be perfect since it is my Grandson's love of the books that led to his interest in London. They will be taking the studio tour later in the week. The suggestions for getting from the airport to the B&B are also much appreciated.

If they take the coach, follow the signs in Heathrow to the National Express Coach station from Terminal 3. No need to buy tickets ahead. I paid 10£ as a walk up rate last May. The bus loading area can be confusing as sometimes the signs are not correct. Best to check with the driver to make sure he's going to Victoria Coach Station.

They'll exit the Victoria Coach station onto Elizabeth Street. They'll go right, pass the Sainsbury's (ATM out front and even though it's not in a bank I use it.), the gelato shop and then you are to Ebury street. It is half a block to Ebury street.

https://goo.gl/maps/47kJ1N2na2n

IF they are on this end of Ebury, the Italian restaurant Sicily which is right beside the Coach station exit has very good food. Especially if the 10 year old needs some pizza! There are a bunch of restaurants on Elizabeth Street on the other side of Ebury Street as well.

I wish I were there, right now. Can you tell, lol?

Make sure you get your Harry Potter studio tour tickets as soon as they are released. They go quickly.