Hammy, Have the wedding you want. Of course you should. It sounds as if it will be lovely and the kind of day that will make you happy.
I wouldn't dream of taking my child to a child free wedding. never in a million years. And if something happened last minute that emant that I didn't have childcare for him, I simply wouldn't go.
DH and I had a child free wedding, and itw as great. Our reception venue seated 80 maximum due to health and safety requirements. If we had invited children of our guests, we would ahve only been able to invite 68 guests. By making it child free, we could ask another 12 couples. We are lucky to have lots of very good friends and close family members, so we really really wanted to ahve as many of those friends there as possible. We went for the friends over the children, and I'm so glad we did.
I have also been to a child free wedding since having DS, and it was great! We arranged childcare well in advance, and I absolutely loved being able to spend the lovely wedding day in adult company with my DH. Perfect.
Stick to your guns Hammy, but definitely make sure that you or your DP has that coversation with the couple in question well in advance of the big day. You don't want them to say something along the lines of "Well its too late for us to organise childcare now, you should have said earlier" as that prolongs the conversation and awkwardness.