S.D.
I know how you feel. I have a (nearly) 18 month old that has lots and lots of energy. But it's too hot to be outside all the time.
Things to try:
Gymboree, Ft Myers (www.gymbroeeclasses.com) - this is excellent but can work out expensive. But check it out.
Tumble Jungle, Cape Coral (www.tumblejunglehome.com) - similar set up to Gymboree.
Coast Elite Gym, Fort Myers (www.coastelite.com) - Has a parent and child class for walking to 3 years old. And Open Gym on Mondays and Wednesdays for toddlers.
Kidz Zone, Fort Myers (www.kidzzone.biz) - An indoor play place behind Outback Steakhouse on US 41. Good fun and they have a small kitchen area at the back so you can take your own food and spend the day there. $10 per day (discounts are available).
If I think of anything else I'll add it.
Hope this helps.