Yay! 
I thought it might be something he'd like. With Kennedy SC, Titanic, Disneyquest (lots of science stuff, design your own rollercoaster and live it out in a simulator), wonderworks etc, I'm sure he'd love it. There's a 'Ripleys believe it or not' but you'd need to go on their website to check out age appropriateness for younger DS.
I've never been on the Amtrak but we are definitely doing it next time we go.
Penn station, NYC to Union Station, Washington DC first (takes a few hours so only require seat tickets) See the White House, Lincoln Memorial, Pentagon, Wasington Monument, Capitol Hill.
Then overnight Amtrack to Orlando the next day. The train won't sleep four in a room though so you'd have to split up but there are 2 room types. Roomette which has bunks, toilet, desk, wash basin. A bedroom has all that but the lower bed is a small double and it has a separate shower room. Each carriage has its own concierge who is available for the entire journey for room service, extra bedding, anything you want really. Great viewing carriages to catch some epic scenery on the way and full service restaurant. Look it up!
Also, they both might like the Intrepid museum in NYC. Aircraft carrier, lots of aircraft on deck, submarine and space shuttle.
Have a brill time!