It seems like he gave himself permission to indulge when you and the kids are away. Like he gave himself a free pass. The fact that he isn't working a program, it's easy to see how someone can self talk themselves into drinking again. Most people do even if they don't have an addiction. I work out 6 days/week, eat a balanced diet for the most part but also give myself permission to have treats. But sometimes I over indulge, then feel bloated, gross, fat afterwards. Why did I have to eat the whole entire pizza? (Well it tasted so good and I couldn't stop at just one slice, or two and by 3 I was like f*** it, I'll deal with the consequences later). I get myself to the gym the next morning and do 3 hours straight. Things like this happen to the best of us. We are only human. The important thing is that he realizes his faults, understands the consequences of continuing and does something to prevent these slips from happening again (ie working a program).
The important thing for you to work on is having a plan. Understanding that there is a high probability of a slip-up and what will you do for yourself the next time a slip or a full-blown relapse occurs? A plan is important. Most times families are under impressions that "the addict needs to now stay sober forever" and if they don't, families will show disappointment, anger, resentment, emotional and mental abuse etc. But that's because we are all human and emotionally driven. You have put all your money on a gamble with the lower probability of winning. Understanding this is beneficial. Pop the fantasy bubble of a "happily ever after family dynamic". I tell myself this everyday. My AH is working a program, looking and behaving much better, is sober. But I never tell myself that this will last forever. If it does, that's excellent. If it doesn't, I'm prepared.