Also will be doing Busch Gardens. Can that also be done in one day?
Oh man...
My wife and I went to BG back in January (low season). We spent 2 full (open to close) and one half (open until lunch) days in the park, and probably would have gone back again if our 2 week passes hadn't expired first!
Seriously... it depends on what you want at BG. If you just want to do all the rides, then a day should be fine. If you just want to see the animals, then a day should be fine. Even if you just want to see all the shows, you'll probably need a full day to make the schedule work out to see them all.
However, if you just want to see one or two shows, do most of the rides, and see a handful of animals, then you can probably do it in a day. It just depends what you want out of it.
Understand, however, that when we talk about seeing the animals, we spend quite a bit of time (especially with the tigers!) The keepers talks are great, but that's another thing you have to schedule in.
In any case, I'm sure you'll have a great time at BG. It's my feeling that BG is sorely underrepresented here on the DIS.