I pronounce
Rowena ro-WEE-na and Rowenna ro-WEN-a. I agree that ro-WEE-na sounds whiny. I like
Rowena pronounced ro-WEN-a, but a lot of people would probably pronounce it ro-EE-na since that is the usual pronunciation, so using Rowenna would make more sense. I don't think that Rowenna is too elaborate. It would at least help ensure that people pronounce it ro-WEN-a rather than ro-WEE-na.
I like
Ravenna. I can imagine people mistaking it for
Rebecca, though. I don't live anywhere near Ohio, but for people who live near
Ravenna, Ohio, it could make the name less appealing even though the Italian City came first.
Out of the three, I would probably go with Rowenna.