Yanbu to want a child free wedding, for any reason. I'm quite jealous actually, I was looking forward to having one myself. However, in my case, we will now have our own there, a close friend will have hers (and probably another by the time we actually get back to setting a date at this rate), leading of course to every other family members' children then having to come.... Anyway, it is what it is. Really don't get the mentality of "oh but it's a family event, how dare you leave out the quite likely to get over excited, runnning around, looking 'so adorable' little mites". Kids and weddings don't really mix, especially when other people's children are not so adorable to you
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Having said this, if you do not want children at your wedding, you have to accept that some people just cannot attend. Most of them are not just 'trying to make a point' because they are so entitled in thinking their kids should be there as well - the feeding, lack of childcare, child is ill and needs a parent at home - many factors can disrupt a plan to attend. Not their fault, I'm sure they would have loved to come, but these are the choices we make when we have children.
So stick to your plan, do not feel guilty, do not make anyone else feel guilty and have a lovely day!