The main 'Bletchley Park' exhibition is good, but it focuses on the human experience of the code breakers. Head around the corner from the car park to the National Museum of Computing (also on the Bletchley Park site) to see more technical exhibitions: they give proper demonstrations of the machines invented at Bletchley, as well as the oldest working computer in the world (which was computing prime numbers when I visited).
We have a few such odd arrangements, such as the "London Bus Museum", which isn't in London but is in fact entirely within a completely different museum, the Brooklands museum.
Operationally independent, although they have been considerate enough to synchronise their opening hours.
If you're interested in London Buses however, I'd actually recommend the (also unrelated) London Transport Museum, as this one is located in the tourist heart of central London in Covent Garden.
( NB: Brooklands is itself a great museum, but more for the aviation history )
Although the London Transport Museum is fun (some years back I decided to spend a week in my own capital city as a tourist, staying in a hotel in the centre, all day looking at stuff with tourists - and LTM is one of the things I decided to do) like most museums it does have a lot of stuff it can't display - but unlike most museums those things are sometimes huge like a bunch of buses, so they're not in a back room they're an entire other site, in Acton IIRC, the Depot, which is in fact open this weekend: https://www.ltmuseum.co.uk/whats-on/depot-open-days
Is Brooklands the place where the corner at the Silverstone racing circuit is named after? It's also known for its aviation history of course.
Yes, there was a race track at Brooklands. Some sections of it are still there including some steep banked track.
I wouldn't skip the main exhibition area. In an era where people were called computers, the human experience was at the heart of the Bletchley Park machine. In the main area, you learn about the makeup of this apparatus: the different roles people had, how information flowed within and between the huts, and much more. There's also a little museum with fascinating artifacts and an area dedicated to Turing. Don't miss it.
Also, and not obvious, because these two entities are distinct despite occupying the same site: they're not always open at the same time. So if you want to see both, even if you plan to spend more time at one than the other, check they're both open.
Whether something is the first computer is - inevitably - a definitional argument, but TNMOC has several candidates (though not all of them) including (a modern reproduction of, the original was destroyed as a secret) Colossus which is famous because of its involvement in the war.
Bletchley Park is also still an actual stateley home, all the war stuff was built on somebody's grounds - there's a good chance you either don't care about stately homes or you're intending to visit a more interesting one (or indeed one of the Royal Palaces), in which case no need to care, but that's a third distinct thing on the same site.
[Edited to make clear there is no original Colossus, we destroyed it because it was a secret]