Oh, I love it! I also love Gaius, just because I have this amazing soft spot for any historical name. I'm not super wild about Vesper, though. It's just too much like Caspar and Jasper, neither of which I like.
Ceres is a town where I live,and I've enver heard of it said: seh-reez. I always say series, and have hear dit that way. It's pretty but don't do goddess names.