should I still do dining reservations and fast passes?
Definitely! As 4yoniD said, they still get very booked up! depending on when you are going, February can be a very busy time (around Presidents week is packed but the rest is low crowds). Certain FastPasses are all gone within minutes of the FP window opening up and if you're staying offsite you can forget getting FPs for Anna & Elsa, Mine Train and any parades/fireworks as you will never get one!
Do these just apply to the Disney parks?
Yes, no other parks have FastPasses. You can buy Express Pass for Unviersal but that's quite expensive.
which rides would you really recommend for DC, 2 boys aged 7 and 9.
Tbh, there are just too many, and such a huge variety, to list! Best bet is to have a look at the parks' websites too see what you fancy as that will give you a better idea.
which are the best parades and fireworks?
Main Street Electrical Parade, Celebrate The Magic and Wishes fireworks (all in the Magic Kingdom) are not to be missed. I don't think much of the other parks' fireworks/shows at all but other people love them.
and recommended restaurants?
Are you looking for onsite recommendations? What sort of food do you like? Again, there are so many that it's really hard to recommend without knowing more of what sort of thing you want.
Have you thought about a water park? It's many kids' favourite parks, they love them (and so unlike anything we have here).