I'm not at all a fan of nicknames.
Sorry if you already said this, but I quite like Tavia (or, as you said, Tavie). Still three syllables, but an easy progression to make, and it sounds so much less contrived than any of the others. It also fits in with other well used names, e.g.
Olivia. (That way your children won't be so embarrassed by their mothers name-nerdiness, which is what I assume you are trying to achieve by having nicknames) Also, Tavie seems to have some about in a similar fashion to
Victoria nn
Tori.
I prefer
Bobby to
Rudy, simply because my mother used to call my sister and I nudy rudy's when we ran around naked after a bath when we were younger (sorry for that, but every time you post it I think that). Buuuut
Bobby is quite contrived (for Rudolph)and I prefer
Robbie as a nn for
Robert.
I also hope
Cordelia would be just that most of the time too. The reason
Cordelia never earned a permanent spot on my PNL was because I hate all of the nns for it. (well, as stated before, I hate the concept of nns altogether, but that is irrelevant)
Mimi sounds ridiculous and sort of...tacky. I prefer
Minnie by far.
To be perfectly honest, I think there is nothing wrong with
Adelaide. I think she could go by just
Adelaide quite easily.