Two night stays in Southern England/London? Too much moving around?

Why don't you try booking.com for research and then you can book directly with the lodging or through booking. Booking offers much more than just hotel rooms.

I was in London for the first time in October and stayed at Hotel 63. It is a 16 room bed and breakfast right across from Kensington Gardens and very very close to very good transportation.

You might be able to book one room for the two adults and one room for the three teens.

Kensington Gardens is wonderful and would be a great place for the more active teens as well as the teen who likes to just hang out.

You can walk to Hyde Park. You can walk to the Serpentine. You can walk to V and A and to a Science Museum as well as a Natural History Museum, across from V & A.

I loved the location.

EDIT. https://hotel63.co.uk/

Try these chain hotels > Premier Inn
Travelodge.

as long as you acknowledge that you get one day of sightseeing in a two night stay - arrive and settle day 1 then night 1 then sightsee on day 2 then night two then leave. It does mean a lot of upheaval and less time to do what you want to do, but it does allow you to keep moving.

Quantity vs. quality - the eternal question.

mrsbunnel, I would suggest trying Premier Inns, which as James mentioned, are chain hotels. But they are very clean, very comfortable and very reasonably priced. They have family rooms available, or you could get a couple of rooms near each other. They have many locations throughout London and the UK. I'm staying in London for 5 nights in mid-March and I'm only paying £140 a night for my room.

I just did a quick dummy search at the Premier Inn County Hall (which is the one I'm staying at) located in South Bank, and found 2 rooms (1 family room, 1 double room) for mid-March for a total cost of around £250 to £320 per night (depending on whether it's cancellable or not). As mentioned, there are many other locations as well. These previous posts might help with deciding on locations as well:

https://community.ricksteves.com/travel-forum/england/requesting-opinions-of-certain-premier-inns-in-london
https://community.ricksteves.com/travel-forum/england/london-hotel-help-for-3-adults-1-with-mobility-issues
https://community.ricksteves.com/travel-forum/england/so-many-hotel-choices

One last note: I would advise you to book quickly as the closer you get to your trip, the more the prices rise.

We are staying in both London and Oxford in May. I would not assume Oxford would be cheaper than London. I did not but maybe March would be different than May.

As others have said, Premier Inns are cheaper further ahead they are booked. My son and his fiance have a Victoria Station one booked for May for less than 120 pounds. They booked before Christmas so not sure what the price is now. It is a very good central location.

I did stay in the Premier Inn that Mardee recommended in 2019 for five nights and really liked the location. It is a quieter area than Victoria Station across the river from Westminster. I think it is ideal for a longer stay but Victoria Station area may be preferable if you stay only 3 nights as it is closer to the sites.

You wrote:
"We wanted to do Blenheim Palace and Oxford as day trips from London anyways, so I'm thinking maybe staying 2 nights in Oxford after Avebury,"

I think this is a great idea. Much better than trying to do Oxford and Blenheim as a day trip. This will give you enough time in Oxford to walk around, explore, maybe take a walking tour of the colleges which starts at the Tourist Information Centre.
The teenage boys in your group will possibly enjoy this a lot more than London.

"Will I really save that much in Oxford accommodations?"
It depends upon what hotel in Oxford you are comparing with what hotel in London.
But saving money is not the point here......I believe you will enjoy staying in Oxford.
Yes, budget accommodations can be found in Oxford.

Oxford has a Premier Inn, and the usual budget chains. Plus B&B's.

"What do you guys think of two night stays? Is it too much moving around?"
No. I like this better than those posters who will only be doing day trips from London so they will only have a couple of hours in each place they go.

As for London hotels, I refer you back to Mardee's post and her excellent suggestions.

Oxford and Bath are two towns in England that have seemed about as expensive as London to me, but that may depend on the price point you're looking at. I'm always looking for the least expensive place I can find that's well-located and has reliable Wi-Fi and (in the summer) air conditioning. But I'd absolutely spend multiple nights in Oxford to have time to see it well.

Excellent advice from all! Thank you!!

Avebury, 2 nights, WHY? You can do that place in an afternoon.

In Bath, a great B&B is the Brooks Guesthouse, in a great location/

Why two nights in Avebury? We are renting a car in Bath to drive to Avebury, then using it as a base for walking around, driving to Stonehenge, Salisbury, and old Wardour Castle. Other parts of Cotswolds too if we have the opportunity. It is also a compromise for the people who like to hang out in nature instead of big city.