Welcome to the neighborhood! I'll be wandering around with my 8-month old strapped on, and "manning" Elfant's table from 2-3pm. Last year was my first time, and it seemed HUGE. Lots of people, lots of vendors & organizations represented, very friendly vibe. Lucky for me, our table was adjacent to Chestnut Hill Nursing Mothers, who run a fundraiser with $1 maternity & children's clothes. I think there were pony rides for kids on the west side of Germantown Ave (Upsala?). According to the website
http://www.mtairyday.org/ this year they've added something called Mad Flavor w/local restaurants. But last year, food lines were long, so you might consider bringing a picnic to avoid the wait. There are nice big shade trees inside the gate of Cliveden to eat & relax under (just don't let your kids play within any yellow tape there). That section of Germantown Ave will be blocked off so traffic will be diverted, and parking might be tough on the nearest side streets. I've heard that there will be activities and a flea market on the 7100 block near Mt. Pleasant as well. May 2nd is also First Friday on the Ave, and Sunday is Chestnut Hill's Home & Garden Festival. Enjoy!
p.s. Mt Airy Times Express published a list of participants:
http://tinyurl.com/69wfrn