Family Vacations

We don't go on vacations. The last real family vacation we went on was about five years ago. We decided to drive up to Maine from the little town in Massachusetts where we lived. Looking back at the pictures it seemed like we had an idyllic time! We drove through Kennebunkport, we saw Longfellows home in Portland, and got pictures of the beautiful seaside towns, but in reality our daughter (then one) got sick and puked all over the car, we didnt pack enough warm clothes and we were generally stressed out the entire time. I think we were traumatized by that experience because since then we only do day trips and tell ourselves we are practicing for when we really go on a family vacation. Now we have two more kids so the prospect of things going wrong has doubled...or would that be tripled?
We have had our share of bumps in the road, things that have made it difficult to travel, but this summer we're hoping to push past those things and take a trip or two. Anyone have pointers on what works and what doesn't? We realize that it is not going to necessarily be a "vacation" for Matt and I, but we're determined to not just sit around. We want our kids to have memories of family vacations. We're thinking of keeping it simple to start with. Maybe a couple nights in San Antonio. Pointers?