How to reject “family” trip

Long story short

My bf lives with my parents and I, we rent out the basement (full bathroom, bedroom, living area, laundry etc…) so obviously he’s super close with my parents

His mom and dad are divorced so he had a step mom. Don’t get me wrong I love her but I can’t stand the way they do things. (Letting their 14 year olds smoke weed and hang out with drug dealers)

My mother, father, bf and I went to Florida for a family vacation this past October, it was amazing! We did 50/50 payment which worked great with our budget and honestly it wasn’t too expensive! We had saved for a year for the trip so we had a lot of fun…

We went to his step moms and dads house for thanksgiving and they’re letting us know they’re taking a trip down to Gulf Shores (Orange beach…. SUPER EXPENSIVE) to renew their wedding vows and would like us to be there. She started out by telling us how she already rented this amazing AirBnB for everyone to stay in, how she wants to take family photos after the vows and stuff. Now she’s planning this trip in June-july, wants us to come down for photos and drinking and partying since her girls aren’t “of age”

Then she proceeds to tell us although his bio sister and her bf will be staying with them (free of charge. They’re only a year younger than us) . (He has 5 sibilants only one biological sister) we will have to pay our own way down there. We don’t have an issue with paying but it’s SO EXPENSIVE and literally this trip would put our lives on hold. We really don’t want to go.

We told her that we are looking for a home right now and also trying for a baby (they know we lost our first pregnancy a year ago). We might have to do IVF pending test results so we’re also saving for that in case worst case scenario. So we only have extra money for groceries and bills. We’re budgeting.

She goes “Oh you guys can just stop that and resume when we get back from the trip, besides if you’re pregnant we won’t be able to drink and have a lot of fun!” That just rubbed me the wrong way.

Like ??????

I’m not putting our life on hold for a 3 day trip for you to RENEW your wedding vows with a dude that’s cheated on you multiple times. We are NOT going to put a baby on hold, we are NOT putting finding a home on hold. We are NOT GOING. Him and I already agreed we can’t afford it. We also can’t believe she just basically said put your life on hold for us.

Like who does that?

Not to mention his bio mom ruined his credit by putting him on her CC as a authorized user without our knowledge or consent, so we’re dealing with that right now.

There’s too much going on for us to plan a trip that isn’t even something we want to do.

I know when we go for Christmas eve SHES going to bring it up again.

How do I tell her nicely we aren’t going to put our lives on hold, we aren’t going we can’t afford it. She always got an excuse or a “fix”….. it’s like she won’t take no for an answer.