So you have added a R.S.V.P to your party invitation, should you expect a response?
Yes you should, but it probably want happen!
It seems to be in the culture of birthday parties, that they will only tell you if they can’t come.
Remember the people at the party are the important ones. you’ve done food boxes for the amount of children invited, so not a lot of food wasted.
If its the Easter, Summer or Christmas holidays and your holding your party at this time? expect numbers to dip.