Bike shop that sells and installs a child/toddler seat?

I've been shopping for one of the child seat/baskets that attach to a bike, and most of what I've read online says pretty clearly "have a bike shop install it".

Can anyone recommend a bike shop in the general park slope vicinity that (1) has a decent selection of these kid seats and (2) can install it for me?

I do have access to a car, so I could conceivably drive somewhere if that's the only option, but somewhere walkable (or bike-able) would be ideal.

Thanks in advance!