proud_canadian, we are planning a DLR trip for this fall, and I have been researching flights since last summer. We will most likely fly out of Detroit instead of Buffalo because of the cost difference. Your choices are basically Southwest for cheap ("Bags fly free!" is going to be very important for a family of 6 with possibly two or three carseats in tow.) or Delta for nonstop. I consider $350 per person, taxes et al included, to be an OK price from my research and $300 pp to be a GOOD, jump-on-it price. Unfortunately, the better prices don't come up until the summer, pretty close to our trip time.
I continually debate if we should pay more to take small children on a direct flight, or if the break changing planes in Denver would actually be better, since they would get to get up and stretch their legs and seeing another airport might be exciting to them.
I would love to fly into Orange County instead of LAX, but that's another big cost difference to weigh. We are renting a car regardless, so LAX's distance is not that big a deal, especially since we have USC (my alma mater) and the Cal Science Center to visit in LA, but the idea of using a nice small airport is tempting. LAX is HUGE, right up there with the NYC airports, O'Hare, and Atlanta.
AJ