Trip to The Tank Museum in Bovington

Alton Towers is over 200 miles from Bovington, in Staffordshire.

That is therefore a day trip from London, a very long day trip..From Bovington a day trip with decent time at Alton Towers would be close to impossible.

Train to Stafford or Stoke on Trent then taxi as there is extremely restricted public transport to the park.
Ideally the previous night would be in the area. You can even stay at the resort.

As for Bovington the main bus service will run from Wareham station.
So try Wareham first. Lodging will be in high demand, so if Wareham draws a blank then try Poole or Bournemouth, both just down the line.
Or maybe the coastal town of Swanage- use bus #40 to Wareham.
Or west of Wareham try Dorchester. There is a nice Premier Inn right by Dorchester South station and bus #X52 from the station should be running direct to the museum.

I think you’d have to stay overnight at Alton Towers. It’s a long way from London never mind Dorset and it really needs the whole day from opening to closing if you want to go on all the rides. What are his reasons for wanting to go to Alton Towers? It does have some good rollercoasters so of he’s a fan of them then I can see the attraction. If it’s just for a fun day a theme park then I don’t think it’s worth it. It definitely ain’t Disneyland.

Dorset is one of the most attractive parts of England and there is loads more to see than just the Tank Museum. The coast to the south - especially Lulworth Cove & Durdle Dor is stunning and not to be missed.

Alton Towers as explained is miles away and your son is suggesting it because he is aware of this place. It would make more sense to go from London to Dorset - perhaps use Dorchester as a base. Then rather than return to London, take a direct train from Dorchester West station to Bath for at least 1 night.
https://www.visit-dorset.com/explore/villages/east-west-lulworth/

Buses for tourists in Dorset:> https://www.firstbus.co.uk/adventures-bus/services/jurassic-coaster

PS. Weymouth is also worth a look.

Thanks for all the information! My son (who is a student of history, with a special interest in WWII) is so looking forward to this trip. His interest in Alton Towers stems from being a rollercoaster enthusiast for many years- although it seems like it might be too much travel for this trip, it's been on his radar for a long time so they'll have to decide if it's worth the extra effort. I appreciate the info on close by towns and potential lodging- it's definitely a help!

Alton Towers has a hotel so you could stay right there. It does have some good rollercoasters. I think Nemesis, where your legs hang loose, is the best I’ve ever been on. I was there last year and it was being refurbed or rebuilt - not sure. It’s open again now. The wooden Wickerman was great and very scary.

First, the Tank Museum at Bovington is a must for anyone interested in armor, or WW2, though the collection ranges from WW1 to present day.

As others have described, it can be done by train to the general area then bus or taxi. I found though a rental car to really be nice for that part of my trip. Much easier to get around, you can spend some time at the shore (Late April is iffy on weather, but many days you could sit on the beach or visit a seaside town)

I get kids and wanting to go to the amusement part, but a history buff like me would gladly trade that day for a visit to Portsmouth and the WW2 and Naval sights there. A full day in Portsmouth is not even enough time to see everything, and Portsmouth is not far, 2 hours or so by car from Bovington.

What you could do, if we want to make dreams come true, is to go to Bovington for the weekend.
Then on the Monday train Wareham to Bournemouth, then the 0945 direct train to Stoke on Trent, arrive 1348, taxi to Alton Towers. Spend the night there.
Tuesday having fun, a 2nd night there.
Taxi back to Stoke on Wednesday, then two trains an hour direct to London Euston.
The direct train from Bournemouth a!so runs at 1045, 1245 and 1345.
That way both generations are happy.

I will let other, more knowledgeable forum members address the Alton Towers part, but here is some information about the Tank Museum area.

First, here is another post on this forum from the recent past, where there was some discussion of the area.
https://community.ricksteves.com/travel-forum/england/first-trip-abroad-2-weeks-for-entire-uk-enough

You are correct that Wool is the closest point with public transportation to the tank museum. However, Wool is very small and there seems to be very few places to stay there. I don't have any personal recommendation for you in Wool. I found a BnB (Google search) - Fingle Bridge B&B - and if you like what you see and they have availability during those dates, I would go ahead and book ASAP. Your husband and son will then need to use a taxi to go to the tank museum from there. Also try AirBnB if you are comfortable using that platform.

If you cannot find accommodation in Wool, I think your next best bets are Wareham and Dorchester. I think anything else would be too far/inconvenient by public transport and take too long to get to the tank museum, but that is my opinion. My husband and I stayed in Wareham in September and we had trouble finding accommodation that met our criteria, but finally ended up with a nice AirBnB near Wareham station.

It is also a very beautiful part of the country that they will be in. They may want to stay another day or two and at the very least visit Lulworth Cove/Durdle Door part of the coast. And Corfe Castle, but I am biased :-)

Given your interest in WW2 history I would stay in Dorchester and include a visit to the military keep museum which has a huge amount of WW2 history.

If you can hire a car it is worth visiting Tyneham - this village was evacuated in WW2 so that the D-Day landing could be practiced there. The villagers were never allowed to return. There is not public transport to the village though.

If you take the train from London (Waterloo) to Dorset - it will have Weymouth as the final destination. Note that these trains split at Bournemouth and that you need to be in the front 5 coaches to proceed west.