I actually don't believe he'd be in Ravenclaw anymore, but Hufflepuff. And regarding his career, I have a fic in mind where Teddy is a trainee Healer, but specifically for children, as I think he would be very good with kids being in the Potter's house a lot of the time and having so many younger family members. (Well not technically directly related, but I'm sure he considers them family.) I think he'd be interested in Healing after hearing stories of his dad as well as just hearing about injuries and such from Harry being an Auror and maybe Ginny getting some Quidditch injuries.
Bumper Cars in Gringotts
Which house do you think Teddy would be in?
Gryffindor, definitely. Although he is very much like both of his parents, Tonks did show some Gryffindor traits during the times we see her in the series. I'm not sure I can see Teddy in Hufflepuff.
Do you think Teddy would be a shy boy, or confident and out going?
I imagine him to be quite comfortable with himself and there fore being confident and out going.
This may sound like a silly question, but I'd really like to hear your thoughts on Teddy's personality...
I think he would be selfless, brave, laid-back, and would hate feeling weak or tapped. Because of his slight werewolf heritage, he gets rather moody during the full moon and when angered he lashes out without much thought of who he might hurt. He would be a very studious student although he doesn’t stress about assignments and tests and he usually gets A’s with a few E’s and would be a prefect.
What subjects/sports would Teddy excel at? Any? Do you believe he's a good student? A great quidditch player?
I think Teddy would excel at academics rather than sports. I think he not only inherited his father's studious mind but also his mother's clumsiness.
And lastly if Teddy ever did find the Mirror of Erised, what do you think he'd see in it?
I'll just agree that he would probably see his parents.