I think MrsBadger is spot on.
My dh is away a lot. So far this year we've had a month away in Feb/March, July he was away about 7 times (can't remember Apr-Jun, but he'd have been away a bit), Sep/Oct away for several 2-days and 2 1-weeks, now he's away for 7 weeks. Now, I'm really not happy with this (but the pay is pretty good, which helps, but doesn't really cut it for me), and it's very hard as we've got 2,3 and 6 year old, live in small village with 8miles to school, and no family within 3 hour drive. But my friends are great, and family do come and help out when needed, it just takes some organising. And it does make some things easier (bedtime is way more consistent!).
When he announces a big trip or lots of short ones, I generally lose it for a bit then come round... helps me cope.
So, if the 2 nights are a one-off, not part of more going away, I really wouldn't sweat it. It is hard with 3, and esp while the little one is so little, but you'll survive and it's really a very little blip in the big picture.
Good luck, don't make him feel too bad.
xx