Tiny Guests and Change of Plans

Looking for some advice: Due to Covid my FH’s oldest brother is moving his family back to the United States and now they will be able to attend our postponed wedding next year. They were not originally planning on attending our September wedding this year. The issue is that they have 3 children (two girls and a boy). Another of my FH’s brothers also has 3 girls and I’d already asked them to be my flower girls. I know that it would not be nice or fair to disallow the other children to be there (we are aiming to have as few children as possible due to safety concerns- rustic ranch with water features and are only including the original nieces to avoid serious family drama); however I’m at a loss about the decision to include or not to include my other nieces and nephew in the ceremony and if I do, how to do it. FH says not to worry about it right now, but I like having a plan. Thanks to Corona I have a year to figure it out. Silver lining I guess 🤦‍♀️