Why no camping? there are so many different types of camping and it’s cheap. backpacking, car camping/tent, cabin camping.
KOA campgrounds offer a cheap and easy way to vacation. from $20 -$65 a night you can have a tent site or cabin with nearby pools, mini golf, activities and there are normally located just outside of big cities and amusement.
Saving money on the accomodations give you more money to spend. We’ve stayed in a KOA cabin just a 7-8 miles from Washington DC ($65 was much better than $200 a night and KOA’s are family friendly)
KOA cabin camping – all you need to bring is bed linens and a swimsuit.
Try http://www.cheap-fun-family-travel.com for travel ideas

Search your states (or any state you wish to visit) tourism website and find things that would interest her AND you. They usually include a price rating system so you can determine if they are within your budget.
If you want to stay overnight in a hotel reserve in advance. Pick a town you want to stay and then search their entire list of hotels and find something attractive and reasonably priced. Also a lot of the hotel chains will give you a discount if you sign up for their points program.
My husband and I went on vacation for 9 days to the Dakota’s, Wyoming, and Montana. We drove and I had reserved our hotels a couple months in advance. By doing this and joining the hotels rewards programs we saved $250 on our hotels alone (we always had a pool and continental breakfast which is also a money saver with small kids).
Another way to save money is to go after Labor day as prices usually drop.
Good luck!