Right now my wife and I just use Google calendar and iMessage, but I can see a time soon when my child can speak, read and type where it might be handy to have a group chat.
Although reading this now I wonder if it would be handy to have this for my in-laws who all live in the area, since right now we all have to coordinate via email.
But how would you deal with losing history? 10K messages is not very many.
I've been using gmail/gtalk for ~12 years -- I can quickly dig up (and regularly do) pretty much anything my parents and I ever talked about. I consider this to be the killer feature (vs, say, hotmail, where I had to keep deleting messages because of the 10MB limit, back in the day).
If you haven't already, shared photo albums on iOS are a really great way to share baby pics with family members without overwhelming your Instagram feeds or having to email all of the time.
Although reading this now I wonder if it would be handy to have this for my in-laws who all live in the area, since right now we all have to coordinate via email.