We love your kids - we really do! But this is a celebration for adults to relax, so please, leave the kiddos at home :)
If your invitation says "and Guest", then yes, if not, we would prefer if it was just you.
Semi-formal, please. Sport coats and cocktail dresses are perfect! But remember, we will be in the mountains in the fall, so it may be a little chilly later in the night, so bring proper outerwear as there will be both inside and outside activities.