A wedding for a good friend? Yes. In fact DH went to a wedding 5 hours away when DD was 2 weeks old ( my mum came to stay with me but we probably would have been fine).
Stag do? Sorry but no. I'm thinking not only are you on 1 income, he wants to pay $2k for the stag do then will probably have to spend money to travel to the wedding also? Somethings gotta give.
Also you will need more help with your older child so he really needs to step up this time around.
Especially as he's said no to work travel, it's s but of a double standard.
I'd laugh and say no way buddy!