E.R.
If your price range is fixed I'd look into town houses/condos. It's unlikely you'll find much in this area that's a decent 3-bd single family. Alternatively, if you're handy you may find a decent sized fixer-upper. Or, to be honest, rent for a while to get a better feel for where you want to live and what you'll need to give on (price vs size vs town).
I suspect you'll be priced out of the housing market in Concord but you might find a rental. West Concord is great as far as small town charm and walk-ability. The rental market is small but you might find something. Check craigslist and boston.com rentals. Or, I'll throw in a pitch for my town, Arlington. It would be a reverse commute to Concord so it'd be 15-25 minutes depending on what part of Arlington to what part of Concord. It's very walkable, good schools, loads of families and stuff to do. Suburban but close enough to Boston to go in easily. Lots of parks and a great bike path through town.