I think crowds will be low during that time. I'd arrive early - plan to be at the gates at least 20 minutes before park opening. They often open the gates early. It make take you about 20 minutes to park and walk to the parks.
We never do table service restaurants at Universal (I don't know why because we do them all the time at Disney). If you want to try table service I would make reservations. Once we tried eating at Margaritaville but it was soooo busy. We've eaten at several restaurants at CityWalk, but nothing to write home about. Our favorite counter service is the Midway Grill at US. It's next to Jaws and has outside seating where you can watch the boats from Jaws go by. They have Nathan's hot dogs and yummy fries.
I think your boys would love:
US: Terminator 2:3D, Shrek 4D, the Horror Make Up Show (this is hilarious), The Simpsons, Men in Black (my favorite ride at Universal), Jaws, Disaster, the Mummy's Revenge, Rip Ride Rockit Coaster
IOA: Hulk coaster (favorite coaster), Dr. Doom's Free Fall, Spiderman (awesome), Dudley Do-Right's Ripsaw Falls, Jurassic Park, Forbidden Journey, and Dragon's Challenge.
I don't know if your younger one will enjoy the thrill rides or will meet the height restrictions, but there is plenty that he would enjoy. Attractions for the younger ones:
At US: ET (our favorite dark ride), Woody Woodpecker Coaster (it's actually fun), Animal Actors show (we really enjoyed this), Curious George play area, and Fievel's playground.
At IOA: The Cat in the Hat (I love this and never miss it), One Fish, Two Fish, Pteranadon Flyers (I've always wanted to do this, but adults can only ride if they have a child that is under the height requirement), Jurassic Park Discovery Center (great place to cool off and relax)