we live in mendham borough (now the township), and im afraid i cant comment on the daycare situation, as my wife is a stay at home mum, so we don't have that issue. for more casual arrangements, though (e.g. evenings, weekends) there are many excellent babysitters in the area (who you can find on any of the usual websites - obviously being sure to take up references etc).
as far as life in the area goes...its a fabulous place to live, which you must already know since you've chosen to move there. we moved here just under a year ago with our two children, who are now just under 3 and just under 2...the older one goes to the montessori school 2 half days per week, and there are also music classes, ballet classes, Pep club, and all the other usual children's clubs/activities available.
you might want to check out the township website, as its got a fair bit of useful info there:
Mendham Township - Mendham Township
i understand its going to be somewhat more challenging for you than it was for us, given you both commuting to the city, but getting involved in those kinds of classes is the perfect way to meet people. we moved here just under a year ago, and already feel we almost have more friends than we can handle!
lovely place. great choice. im sure you'll love it!