Chatham Dockyard is a really good place to visit, just don't bother with the rest of Chatham its an absolute dive of a town... After your visit head to Rochester instead to finish off a good day at the Docks with some nice little pubs and the Cathedral.
Spent many a weekend on the White ship "Gannet" when I was a trainee at Daedalus, it used to be in Gosport near the Jolly Roger pub. We had to work 1 in 4 weekends chipping paint and helping the restoration effort. I believe it ran out of money and ended up at Chatham where they did the work.
Get yourself a classic car and get 2 adults for a tenner during the Chatham steam fest, been there loads of timed. Our use the side gate at the back of the car park and tell them you are going to the model shop