I have already sent out invites to everyone for our wedding in two months time. I addressed the envelopes to just the adults so it was clear kids weren't invited. My fiancé and I have been undecided for awhile on whether to invite nieces and nephews (all very young.) We ultimately chose not to but I'm now having a change of heart for various reasons. Can I ring our siblings and say we've changed our mind and nieces and nephews are now welcome? Is this rude considering we initially made clear they weren't invited?