My FSIL & FBIL (who we have very little to do with) will at the time of the wedding have two unvaccinated children (aged 2 and under). There has already been drama and tension since my other FSIL & FBIL (who I have become very close with) have kids the same age who are vaccinated and it's led to some really awkward and angry conversations about splitting holidays etc. I have two nieces who are older (5&3) who despite living out of state I am very close to and they are VERY excited about my wedding. They are old enough to fully understand whats going on and I really want them to be a part of my special day. My sister has already asked if the unvaccinated children will be there that day and my FSIL who's little ones are vaccinated has already said she would have her parents take her kids so I don't have to worry about it.
I guess my question is how to I tell my one FSIL that her kids are not invited due to not being vaccinated without it blowing up into a whole issue? I can't say its a kid free event because my sisters kids will be there. I don't want to start anything and my fiance says theres no good answer and doesn't know what to do. I also don't want this to come across as my nieces are invited and his nieces/nephews are not.