We love your kids- we really do. But we regretfully cannot accommodate them at the reception venue due to restricted numbers. We hope you will see this as an opportunity to let your hair down for the night and enjoy the party with us!
If your invitation says "and Guest," then yes, if not, we would prefer if it was just you.
Semi-formal/ Formal, please. But we want you to feel comfortable, so if those shoes are too high or that top button is too tight, let it all hang loose!