Hey Alison, good for you. I'm glad you decided to plan something for you. Make sure you fill your time up whilst your away. Book spa sessions, theatre tickets, movies, galleries. Doesn't matter what. Just make sure you keep busy.
I work on projects. There is always a crises if you look hard enough for one. Your H sounds like the type of person who hides behind his work. Crises' make him feel important and needed. But they happen every day on every project and everyone copes: systems sh!t themselves, a vital script doesn't get run and millions of pounds are about to end up in the wrong account, a requirement was missed and now the company ABC is going to get fined a shed load of money by a regulator. I will say it again, he is hiding behind his work because a) it validates his need to be important and b) it allows him to avoid having difficult conversations.
Anyway, when you speak to him about going away, don't ask, just tell him. It is school runs, dinner and homework FFS and it's only for a couple of days. He can manage that. Thousands of us manage it every day and still hold down demanding full time jobs.