I have no problem with child free invites, but this:
Quite a few of their friends with children had previously indicated that they rather liked child-free invites as it gave them a rare opportunity to let their hair down is disingenuous, because if children are invited I can chose to not bring them (if I can arrange childcare) and "let my hair down" - I don't need to be invited to a child free wedding to do that!, people who have child free weddings need to be honest and own it, and say that that's just what they want, then that's fine! however if the invite is phrased as if they are making out as if they're only doing it to do me a favour - it'll get my back up I"m afraid, because it's not true at all!