It would be hard to underestimate how important vacations are for me, so I want you to have a good one. That being said, I have a question about what you are looking for (in addition to JaneSmiths: what are your geographical limitations):
Your title says "Nature vacation ideas", but the things you mentioned (two water parks, an amusement park w/ some animals in it) are not quite what I think of when I think of a nature vacation. So are you really looking to be in nature, or are you looking to be outdoors? Were you picking Orlando because it is close, or because you want to be warm? Let us know what you're thinking, and I'm sure we can come up with some great ideas for you.