Hi R.,
You are clear that you don't want to go to this event, but it sounds like your fiance had not actually made a firm decision about going or not going when his friend called. It sounds like he might have still been considering going.
Some people have trouble making decisions - they prefer to "leave all options open", which can come across as non-committal and indecisive. When every option is kept open, then we actually are not doing anything but waiting to see what happens next. Then decisions are made for us, which in some ways lets us off the hook in terms of taking responsibility for them.
Or ... he might just have trouble saying no, although by you offering to make the call, you gave him the option to have that stress alleviated.
Either way, it's really not cool for you to be the "bad guy" on your own birthday!
I hear you - your man is climbing the walls, waiting for something fun to do, and maybe keeping his options open in case you want to do something that he'd rather not do. You are being extremely flexible, kind, and generous in telling him he can go without you. (I wonder if that is truly how you feel? Do you really want him to go??)
To tell you the truth, my feelings would be hurt if the man I love chose to do something without me on my birthday. Maybe that's just me.... but it seems insensitive, self centered, and lacking in empathy to even consider going without you on your birthday.
BTW, it's totally reasonable not to want to hang out in the freezing cold with your baby in tow. (I am curious if this is your fiance's son? Does he have children? I'm not sure how long you've been together, but he may not understand how much of a pain it is to cart a freezing cold - and likely a bored - one year old child to this sort of event...?)
I hope he will think of you and what YOU would like to do since it's your birthday. He can put his own needs and desires aside for one day to celebrate with you. That is a reasonable expectation of someone that loves you.
I would be sad if he "blames" you (i.e. R. said we can't come." - that is SO lame! You're his partner, not his mom! If he keeps doing stuff like that, you two may have to have a serious heart to heart ... after your birthday of course!)
I hope he thinks this through and decides he *wants* to stay with you this weekend. I hope, if and when he tells his friend he can't make it, that he will say "I want to spend R.'s birthday with her, and it won't work out for all of us to come this time, but thanks so much for the invitation!" I hope he will *want* to help you plan something special and fun that everyone (including your son, if you'd like) can enjoy. His friend can wait for another weekend to hang out with him.
BUT we can't force someone to want to be with us and to want to create a special day with us on our birthday......
SO..... if he's chomping at the bit to go, and you can tell he will resent missing the opportunity, maybe you can split up the day in some way so both of you can have some of what you want? That may be a good compromise.
This is also an excellent peek into what married life will be like with him.
Just my thoughts! Hope it helps!
Whatever happens, I hope you have a truly HAPPY BIRTHDAY!