GMTA, Phil! That's exactly where my mind went, and exactly my thought on the budget!
I would go to Mara, since it is counter service. Haven't been in awhile, so have no idea what I would have, but figure it would be more reasonable in price than a TS. They used to have a wonderful carrot ginger soup - if it's still available, I'd get that.
For TS, I would be torn. I've never eaten or stayed anywhere at Kidani (just looked around there, and it's awesome, the animals are even closer than at Jambo, which I LOVED!) and I'd love to try the bread service @ Sanaa. However, I've always enjoyed Boma - whether for breakfast, or dinner. And while Jiko is awesome, I love the idea of getting exactly what I want, as much as I want at Boma - so I can try a BUNCH of different stuff. For that reason (and the zebra domes, of course!)

, I'd go to dinner at Boma. I actually talked by phone to the extremely nice pastry chef who "invented" zebra domes years ago - he made a huge custom one for my friend's birthday for me, instead of a cake. He even invited me to tour his kitchen sometime. Never forgot that (or him).