People above have given great advice so far. I'll echo some of the stuff said.
The security, for the most part, is a joke. I've thought that every time I've gone in there, and if I'm honest, is part of the reason I think you'll see some sort of incident there in the future.
They will search bags, they won't have you turn out your pockets. They look closer during major events like HHN, but don't worry about it. Normal days, I've never been wanded or searched.
If you have passes for two days, that's going to make your experience a whole lot easier. I can't remember if they have fast pass or not, but that's always a help. I know money is tight though.
I used to have a season pass, but when I had it, only half of the Harry Potter attraction was built, ie. the Islands of Adventure side. I think there's an Ollivanders in Hogsmeade (IoA) as well as Diagon Alley. But I haven't been to DA yet.
I thought the food was expensive and fairly dull at the 3 broomsticks...I'd avoid that if possible.
The rides themselves are cool. Hogwarts has like a live-action/simulation feel to it, which is kick ass. There are also 3 roller coasters: the something hypogriff for young kids, and the Dragon Challenge which is two coasters the "duel". It used to be called "Dueling Dragons," and its basically the same thing. Its an awesome ride, but not for little kids.
Not sure about the Harry Potter stuff in Diagon Alley or the train ride because they weren't built when I had my pass.
Now, regarding the rest of the park attractions, I am more familiar with those. There's more action in IofA I think. The Hulk roller coaster is pretty amazing. There's also a jurassic park themed splash mountain, as well as another log flume ride and river rapids. There's a spiderman simulation type ride and a free-fall thing there as well. More kid rides in suess land. The Atlantis attraction used to be cool, but they cut the budget alot and changed it so its not as interesting as it once was IMO.
Universal Studios has alot of classics. ET, Jaws, Twister, Earthquake (though I think its called something else now). Those are really just experiences, not really rides. The Mummy is absolutely badass, my favorite ride in both parks. Its a roller coaster in the dark and though it doesn't go upside down, it has a few surprises in store. it's awesome. MIB is cool too I guess...its an interactive laser-tag type ride. All arfcom guys should love that one. The Rock n' Roller Coaster is really cool too...smoothest coaster I've ever been on. Stay away from the Simpson's ride...it sucks so bad. Not sure about Shrek...i really can't remember what its about. And i can't remember if Terminator is still there.
The lines really depend on the day. I've been to the parks when no more than 5000 people were in them combined and you literally walked onto any ride you wanted. i've also been to them when they have been slammed. I'm not sure what to tell you regarding those particular dates. I can tell you that they do have single rider lines that speed up the process if you're willing to break your party up or if only you want to go on a specific ride.
The restaurants around citywalk there tend to be pretty good, but pricey from experience. Expect $15-20 a plate i would think, not including alcohol.
If you have any specifics, we can guide you a bit further.