to expect DH to go to a party that he has accepted an invite to?

DH and were invited to a special reunion party by a very good friend of ours. On balance he is "my friend" (although i hate to divide it like that and DH thinks he's great). We haven't seen him for ages and there will be lots of people there we know, it's a Eurovision night, fancy dress, he is kindly supplying all the food and drink. DH and I were both looking forward to it. I accepted the invite for both DH and me (after speaking to DH) and our friend has arranged for us to stay the night at his place to save us trecking home.

Then I get a call this afernoon from DH. Another friend of ours has announced he is having an engagement party on the same night and DH is saying he will go to friend #2's party instead and "I can do what I like". Friend #2 is a lovely person too and also (I suppose) more a friend of mine than DH. I think what I am trying to say is that DH and friend #2 are no more close or better friends than DH with friend #1. DH simply thinks #2 will be a better party. DH is no wallflower and he mixes with everyone, so it purely selfish.

i like both friends enormously and would definately go to both parties if we didn't have the clash, but I feel strongly that am not letting friend #1 down and neither should DH. The two parties are miles apart at the same time and one is fancy dress, so it's not possible to combine the two.

I feel strongly that if you accept an invite to a party you should go (failing disaster) and explain the reasons and apologise to friend #2. I don't think it is right to cancel friend #1. DH solution is that "we split up" and I go to party #1 on my own and he goes to #2. i normally have no problem going to a party on my own (I can mingle fine without DH), but I think it would be very odd ("X is at another party tonight!") and is a snub to each of them.