>>>Ideally we would like to explore the surrounding areas as well as the parks.
I assume from your question that you have never been to the Orlando theme park area before.
If so then you need to understand that the theme parks are scattered all over the place (even within Disney World), so wherever you stay you are going to have to make a possibly long shuttle bus / taxi trip to the resort.
And being the USA there is not a huge amount of public transport, so having a car makes the holiday so much easier.
When I was there they had a bus that run up and down International Drive called iRide that takes you to SOME of the resorts, but by no means all of them.
I think the only "theme park" you can walk to is Wet and Wild which is on International Drive, the rest you need to get to them with a shuttle bus or taxi.
And you say you wish to explore the surrounding area, but this may be difficult without a car because, as I said, public transport is very limited.
Here is a map that shows you how scattered the theme parks are. Number 3 is International Drive. You can see that Universal and Sea World are fairly near (but not within walking distance).
But look on the left to see Disney World, and look how large it is, and look how far away it is from International Drive, probably about 10 miles (depending which resort you go to).
http://www.disney-villa-rent.com//wp-content/uploads/2010/08/map2.jpg
So it is important to understand the scale of things when planning where to stay, and what you want to visit.
And if it is at all possible to hire a car while you are there then you should consider doing so as the wait for shuttle buses to get you there AND get you back, can be quite long.