One thing nobody mentioned here. If going on vacation, and going to Mass will cause serious disruptions (as traveling with small children can do), it is always possible to ask one’s priest for a dispensation of the obligation prior to leaving. He may or may not agree, but there’s absolutely zero harm in asking.
I have done it before. Once I was participating in a charity bike ride to raise funds for cancer. It was a 2-day, 200-mile ride. Clearly going to Mass, while theoretically possible, was going to be difficult (I could have gone to a Saturday evening Mass after arriving at the overnight campsite, but needless to say after riding 100 miles I was not in top form…, and I had another 100 miles to do the next day). I spoke to my spiritual director of the abbey I am associated with prior to leaving and he dispensed me of the obligation. Of course I was doing charity work… so maybe that’s different, but one can ask.
If the priest refuses then one is to try one’s best to get to Mass. If circumstances beyond one’s control (such as getting lost and missing Mass, a sick or extremely cranky child, or a flight delay causing one to miss the last available Mass) intervene, then there’s no sin involved.
