OP, what he has done is really hurtful. He's been an absolute arsehole to be quite frank.
I totally get you trying to think of some ideas to make his birthday special, thats not controlling at all (someone said that! wtf), its being really thoughtful and taking the time to suggest some things to him that he may not have thought of. I'd appreciate it if my DP made some suggestions of fun stuff for my birthday, it means they care and are thinking about wanting to make me happy.
Unfortunately i too agree he probably had this already planned which is why he was reluctant to engage with your suggestions. wonder when he was actuually going to tell you! And I also bet his mates are seeing it as a bit of a stag do combined birthday event. Which is likely why their partners are possiby having to ok it - its x's stag do, we have to go blah blah.
A whole weekend away for a birthday when you have a young family and not flush with money, and only been married a couple of months is incredibly selfish, at best.
The way he has gone about it is a whole other level. He has not discussed it and to boot insulted you to justify his reasons for going!
He has totally disregarded you as his wife and your family just so he can go on the piss for a weekend, which will drain your finances by the sound of it. And you have no say n it. II'd be really really hurt if my dp did this.
In fact Id find it very hard to get past. Totally understand he wants to celebrate with friends, but there are ways of going about that without insulting and compltely disregarding your wife and family.
If he does in fact go ahead, will he be spending from the joint account? I'd be so tempted to take a load of money out of that account right after he leaves for an 'emergency' purchase so hes bloody skint the whole weekend. And certainly don't get him a present. He doesnt want to send his birthday with you, in fact hes basically said you'r boring, so why the hell would you get him a oresent!
So he leaves on his birthday, is that right? I'd be waking up that morning as normal, not mention a word of happy birthday to him.
I'd also be wondering what sort of 'fun' they will be having in edinburgh thats so incrediblly important that its worth him completely shitting on his wife for. He can get wasted any time he wants, but I'll bet this isnt just a piss up weekend. So sorry OP, but it appears he has very little respect for you.
He could of had his weekend with the lads the week after or before, with your blessing, no doubt if he'd not been a total arsehole about it. I''m so angry on your behalf.