@FunkySnidge. I have a similar situation. But I told the mother of the groom that I couldn't go, as it's an overnight event and my own parents will be away, so no baby sitting option. Now the mother of the groom wants to approach the groom to state my case. Which I do not want her to do. I do not want to be the one creating a drama. Yes, I'm upset I can't go. Very upset, as I even found and booked cheap accommodation for us (thinking I might be able to go), which other family members have now booked. But I don't have an option for my son for 1.5 days we will be away for the wedding. Even if we leave right after the speeches, and don't stay overnight, minimum time for a baby sitter for us is 10 hours. Anyway, time is irrelevant as I can think of no-one who can do it. Yes, I could pay someone, but I wouldn't enjoy myself leaving him with a stranger either. I wish I had not said anything to the mother of the groom, as I am now petrified she will "put her foot down" and ask him to change their wedding rules. I would suggest you keep it quiet for a while and then around the time of the RSVP just reply as 1 going, should DH feel he really needs to go. Let the B&G work it out for themselves that the reason you can't go is baby sitting. Perhaps later in their lives they will understand when they have their own kids. Let them be blissfully unaware of this side of parenting before their time comes. Let them enjoy the day as they had planned. They can learn these things when they have their own kids. I agree with @Mothership4two, pre kids couples are not aware of the issue of baby sitting. And really, I am happy for our B&G to remain naive about that. They are young and they can learn how hard it is when their time comes. Although they will have plenty of choices for baby sitting, unlike me. Even close family have suggested I get a sitter at the hotel. I can't leave my kid with a stranger in a 2.5 star hotel for the night. My son and I will probably go to the ceremony which is 90 min away, and then come home. I am thinking I won't be the only parent in this situation. I am just hoping the mother of the groom keeps mummmm...
I also feel, if they have those rules, they need to be prepared people will have to decline the invite. On my side I think they will be glad I am declining, as they have over-invited for their venue size!! Unfortunately I am collateral damage of their restrictions. But I'm a mum first, extended family member second.
All the best figuring out your situation.