I think you've got a lot of good suggestions of things to do. As for saving money while you're in the Disney parks, I can't stress enough how great it is to bring your own snacks (and lunch if you can fit it in the backpack) and a refillable water bottle! My husband and I took our 2 kids in April (3.5 year old and 9 month old - I'll admit: the trip was just as much for me as it was for them at those young ages) and I calculated that we probably saved $24 each day by having our own water (which costs about $3 per bottle in the parks). We were there during a week where temps reached the mid to high 80's so water was important. The water fountains around the parks allow you to refill as often as you want and I was actually surprised that the water out of the fountains was always very cold and didn't taste funny.
As for snacks, I made sure to buy yogurt tubes and put them in the freezer of our condo. Then I took them out each morning before going to the parks so that by the time the kids were ready for a mid morning snack or lunch, the yogurt had unfrozen and was the perfect temperature. You can do the same thing with grapes for a snack or supplement to a meal. Obviously, crackers, etc, store well too and are good for both snack and a meal supplement (then you just have to purchase a burger or sandwich to go with it).
My other advice is to eat your breakfast in the timeshare. We just had cereal and fruit each morning which was less expensive and healthier than eating in a restaurant and MUCH less expensive than picking something up in one of the parks. And since you'll have your own car, you can find a close grocery store to visit when you arrive so you can stock up (make sure to reserach one before you leave - that will help you avoid shopping in a more expensive but easy to find convenience store).
As for souveniers, we told our daughter on the first day that she was going to be able to pick whatever souvenier she wanted on the last day (with a dollar limit, of course!) This helped to avoid a lot of the "mommy, can I have this" questioning. Or, at least when she did ask the question, we would remind her that she was going to be allowed to pick one thing at the end so she might want to wait to see what else was available. And then when she was finally able to pick it out, she really cherished it because she'd put a lot of thought into it.
Swimming in the pool is always a great, free activity. And we loved the Kennedy Space Center as well (just over an hour drive out of Orlando) - we didn't do it this trip but my husband and I did it a number of years ago before we had kids. A couple good unofficial websites to visit to get tips are mousesavers.com (for money-saving tips) and wdwinfo.com (for general information, including park hours for the days you'll be there since the hours do change quite often).
Most importantly, have fun!!! Even doing the Disney parks with two younger kids, it was honestly one of the most fun vacations I've taken. I was anticipating it being a lot of work (due to our kids' ages) but it really was just a lot of fun :)