forget the babysitting remark, and the sister (you aren't similar at all, she can still adopt, while you reject the idea). At this stage I am confused why you are both bothering to get a ceremony.

Marriage is nothing more than a legal frame, that would help a judge take the fair decisions when the couple is facing a crisis. This is particularly important when kids are in the middle of the divorce battle. There is also dispute over loans and financial maters that need a neutral pov, and the marriage is a protection for the weaker partner.

For me, there is no need for marriage if kids aren't an integral part of the plan. Maybe the United States is different. But more than half couples in France will be unmarried as they have their first child. -- if you are thinking gay marriage right know, I would argue that one of the main reason it was necessary in France, is to force public institutions to recognize adoption procedures, especially of the partner's kids. Gay couples, even in civil unions, were having difficulties picking up kid from school, because the system wouldn't recognize parental authority on the partner's kids --

So if this marriage is just about financial union for tax advantages, and the right to sign a DNR for your spouse, why is there a ceremony for 132 people? Wouldn't filling the proper paperwork be just enough?

I feel if you want to get your in-laws on board for this ceremony, you have to explain what this marriage means for both of you. They are probably conservative people that view marriage as a milestone preparing for the next generation. You have to tell them that their presence at the ceremony is a sign of support for the future of you. That even if things will not turn as they envisioned on some matters, that you still want them part of you life. You future husband would pick better phrasing than me to win them back.