Bearing in mind here that I don't have kids, or own a home, my fiance and I recently made a move from DC to Chicago. On the financial side, what we did was make a two column table, with DC on one side and Chicago on the other. We created a line for every single item in the budget, and weighed out what the savings or increase would be and put the amount into the appropriate column (example, rent is $500 cheaper in Chi so we put $500 in the Chicago column, gas/electric we expected to go up about $25/month so we put $25 in the DC column). Then, we summed each column to see the true change we would have on a monthly basis. After that, we added up all the potential costs of moving (we were pretty close to accurate based on our final numbers). We calculated a break even point of 6 months, which for us was enough to push us to move.
Other things to consider: if you can get a job before moving, your move is tax deductible (without itemizing). If you itemize, you can also deduct the costs of travel for job searching. This can take a lot of the bite out of the costs. For us, the monthly savings was greater than what we calculated because by moving & freeing up so much cash, we were able to pay almost $1000 extra/month towards student loans.
Frankly, all other things being equal, if I could buy a house for $100k less and on top of that be closer to family, plus all the other benefits you mention, I would move in a heartbeat.
