Fh's Sister & sil Are Upset About Children's Rule

So, my FH and I decided to have no children under 6 at our wedding. We made this rule because 2 of his nephews are absolute DESTROYERS and their mother allows them to do whatever they want. We chose the age 6 because that age won't split any families up. FH has a large family (he's the last of 9), so having an adult-only is out of the question for us and this was our best option. Also, we do want our nieces and nephews there because it'll break some of their hearts if they found out they couldn't come.

Anyway, so his sister (the one with the destroyers lol) and his SIL were complaining about the rule and tried to suggest that we pay for a babysitter. You can call me what you want, but I didn't hesitate to say HELLLL NOOOO. Now I would have if my wedding was far but my wedding is local and is just a short drive. I am even having a Sunday wedding because they believe that the sabbath is on Saturday.
And what's crazy, the ones that are making the demands aren't even close with my FH and only talk to him when they need something. His own sister didn't claim FH as her brother for the majority of his childhood because he has a different dad. Like, you've got to be out of your whole mind.
Also, the sister's own husband is not going to the wedding because he doesn't participate in anything family-related, so why not have him watch his own kids? And his SIL has plenty of local family members that already watch her child now, so what makes my wedding day any different? Chile, I cannot.

Anyway, what are your thoughts? I'm not gonna budge and pay because they have 10+ months to figure it out lol but I would still like to hear your thoughts 😁.