Hello, Jessica!
Oh, my, you have selected three wonderful choices here!
On your Animal Kingdom Park day, all three of your options, Boma, Sanaa and Rainforest Cafe, are all easy to access, although Rainforest Cafe is right there at the entrance to AK. Getting to Sanaa or Boma won't be a problem either, because each one is a quick bus ride away at Animal Kingdom Lodge (Sanaa at Kidani Village and Boma at Jambo House.)
You know how wonderful
Sanaa is, especially with that fantastic view of the savannah, so that's a known great selection. Having never tried
Boma, however, you might want to dine there. Much like the flavors at Sanaa, Boma really has an authentic African feel to it, except in a buffet. I see from your other questions that you'll have little ones with you; I always love a good buffet when there are children with us, since the food is right there, ready to be enjoyed upon your entry. Not only is there no wait for your food, once seated, it's also a great way to broaden the little ones' culinary horizons, since they can actually see the food right in front of them, much of which looks and tastes great but sounds a bit scary to an unadventurous eater. Just in case, though, the kids' buffet area serves up standard, typical kids' food, so everyone is sure to be very happy.
On the other hand,
Rainforest Cafe at Animal Kingdom is a blast, and the food is very nice as well. You won't be disappointed here. However, if you've tried a Rainforest Cafe already, you might want to try something that you can't get back at home.
In short, as much as I love Sanaa, try Boma this time. You might just find a new favorite!
Enjoy! Send more questions as you think of them; we love to help!