I have a season pass and, honestly, the main reason I use it is for Hurricane Harbor. My best friend and I go all the time and we go to the water park and then go on the carousel on our way out
If you have a car, I'd suggest packing a lunch in the car. Food is even more expensive there than at Disney, and they also don't allow you to bring in outside food or drinks, except baby or medical needs. You can't even bring in an empty water bottle unless you hide it in the very bottom of your bag and hope security doesn't find it (in which case, make it plastic or glass, not metal). Just get your hand stamped before leaving and make sure not to rub it off before it dries and you'll be able to go have lunch in your car for much less than it would cost to eat in the park.
Buy your tickets online - not only do you get the kids' price (I think that's still going on), but you can skip the ticket booths and go right to the line to get in.
Plan to get there at least half an hour before opening. The parking lot entry will be a gridlock if you get there AT opening. Also, basic parking is $15 and is in the FAR lot. "Preferred" parking is in the closer lot and is $25
My best friend, who I normally go with, has season pass parking, so we always park in the preferred lot. Much easier.
Don't bother with the Flash Pass. In my opinion, it's a waste of money, especially if you get there at opening and hit the big rides then.
If it's hot when you guys go, definitely go on the carousel and sit up top. There's a fantastic breeze up there
There are very few rides where you can carry something on, like a backpack or whatever. The "bigger" rides will have lockers outside of the entrance, but they're $1
per use. Aka, every time you open it, if you want to still use it, that's another $1. If you want a locker all day, I think the cheapest one was $11 and it was fairly small.
Also, I don't know if this applies to you and your family, but most of Great America's rides aren't exactly "size friendly". I'm a bigger woman and Viper is an extremely tight fit and I barely fit on the Eagle. I haven't bothered with any of their larger rides (Iron Wolf, Batman, etc) since high school, because I went on Batman once and the attendant literally jumped on the harness and then YELLED at me not to come back, which humiliated the crap out of me (seriously, 16 and already body conscious, didn't need that, he could've just been polite and asked me to wait for my party at the exit).
I'm trying to think if there's anything else I could say, but I'm drawing a blank.
