I'd go. Keep to a strict budget without a lot of extras that cost $$ and make sure your DH is on the ball about looking for work, but it sounds like you have some savings, you won't be completely tapped because of the trip, and he's got quite a bit of advance notice as far as finding new work. As you said, rescheduling for after he finds a new job might be very difficult (most of the jobs my DH has had don't allow employees to take vacation until they have at least a year in), so even if your airline is willing to let you have a credit for the tickets it is possible you won't be able to use it before it expires.
Personally, I'd economize like crazy, find every corner to cut in the budget, save every penny I find on the ground (well okay, I do all of that anyway), but I'd still take the trip.