would blood orange be okay with this? e.g. it won't add bitterness compared to a navel orange?

Thanks for the help!

I don't think of them as bitter either, maybe a bit more tart, like tangerines are more tart than oranges, which I like. Go ahead.

It would be delicious and traditional. See for example http://food52.com/blog/9053-fennel-and-blood-orange-salad

Personally, I've never thought of blood oranges as bitter, but more rich than navels.