When we go on our trip next year, my two friends are going off to discovery cove for a day but im really not fussed. I'll be able to get to any Disney park for free and have enough days on my ticket to do a couple of parks that day, or something completely different....what do you suggest?

that you want to go back to then you could go there in the morning
. Or maybe you could do one of those tours of the parks that are offered. You get to see behind the scenes kind of stuff
. DTD is a day in itself (the marketplace, the west side) 

