NTA

It's your wedding. If you want to hear your ceremony and vows without a screaming baby, or enjoy your reception without kids you know have poor behavior acting as they always do - then you will have to tell your siblings "I'm sorry, we will miss having you there then".

It is their issue that they don't want to find a sitter. Most adults with kids WELCOME having an adult event where they aren't constantly looking after (or worse, ignoring so someone else has to deal with) their children.

You don't have to explain why. You're not there to accuse them or make implications about their parenting. There's no kids except the ones who call you Mommy and Daddy (but stick to that - NO EXCEPTIONS or it will be a war). Cost, rules of the venue (many don't allow kids), wanting to enjoy your day - all of that are valid.

One thought -what if you got a sitter and your kids saw the ceremony but left at bedtime? (just in case you want a compromise).

Good luck, at least in my family it all blew over after my (child-free) wedding.