The trifecta of rude guests:
1. Unwanted kids
2. Asking to bring more people
3. Bringing an uninvited guest
OP handled them all politely and firmly. Well done!
Oops! You forgot the "I need a ride!" invited guest!
Anyway, the update is glorious. Actually, if John had been polite, would you have let him stay? NO! NOT Glitter! You had plenty of room for him after the other last minute decline, but you stood your ground.
If our parties were more...partyish?... I would so be taking lessons from you! Kareoke? Really? Good for you!
Congratulations! And, to me, it seems espectially important that the little girl understood! Cookies? How sweet, both dietarily and in personality.