Like most posters, I think you can eliminate a lot of clothes. When we drive to destinations, we tend to get lazy and overpack for all contingencies. So now I pack what I think I'll need, then unpack half of it--and I'm still overpacking! Your individual wardrobe items should all coordinate with one another and work as layers, so you can adjust to the weather accordingly. Sure, it may be boring, but who cares if you end up wearing the same sweatshirt every day?
I also recommend doing laundry halfway through a trip; I always take an morning/afternoon/evening away from the parks and do laundry. You'd think it would feel like time wasted, but it gives me some down time to rest, read a book while the laundry's being done, and return to the parks refreshed. (Shhhh...don't tell anyone, but I even do laundry the night before we leave, so most of our clothes are clean when we get home.) Do bring, however, two pairs of good walking shoes to alternate.
Other space savers: I agree with other posters that might consider buying food once you get there. Sure, you might need to face the local Publix, but it would give you extra space. And I find the prices in the area slightly higher than my home, but not so much that I would bring too much stuff with me. (Exception: I have some foods that I eat that aren't available everywhere, so I bring those with me.)
You can eliminate the need to bring bottled water, if you do so, if you invest water filtration systems. (Bring a Brita pitcher instead of bottle water and refill.) You might also consider shipping things to your hotel, although it seems like you're also looking for cost-cutting measures.
Eliminate or seriously minimize the toys/traveling distractions, both for your party's children and adults.
I'm sure you'll have a great time, and lessening the amount of stuff you bring will help you maximize your trip. Good luck!
