Since he's a little older, I'd go with a center. They tend to have lots of age-appropriate activities, other kids his age, etc. I wouldn't bother with a nanny share--go with an in-home or a center.

From my own experience, I personally liked the in-home daycares over the larger centers, though both are good places for kids. My son enjoyed more personal interactions in the home daycares and his providers did home cooked meals instead of ordering catering. With a small group of kids, home made meals are definitely easier.

Having said that, larger daycare centers have more play spaces and more opportunities to meet new people. The webcams that some provide are a great way for you and extended family to see the child. No matter what you choose, be prepared for a few months of sicknesses from daycare. The home daycares are slightly better due to fewer kids. Though all it takes is for one or two to get sick before infecting everyone else. Even the providers can't escape it. The good news it will all pass and the kids build great immunity.

I have a two year old that has been at home with his dad up until now. I am so thankful that he's been able to spend his first two years with a parent but it is now time for dad to go back to work and for him to get more social interaction. (Dad goes to the library or park daily where there are nannies and other kids, so he does get some social time now, but not a ton.) We are trying to decide what is the best type of environment for him as a two year old entering day care for the first time. Would a nanny-share offer any real social benefits over being home with dad? Also, I'm trying to figure out if an in-home daycare center with 9-20 kids (I am looking at 2 different places, one with 9 and one with closer to 20) is really any different than a larger center that is divided into rooms with the same amount. Any advice would be much appreciated!