I promise I’m alive, and here with the final installment for throwing a surprise party!
So to start, with the party itself, you should be talking with the birthday boy or girl, several weeks out laying foundation work so you can manipulate/verify timing. I suggest saying
“hey I got reservations at your favorite restaurant for this time” and then on the day of you can drive to the party location and say “oh I just have to drop something off here…etc”
Basically help be in charge and say oh I’ll invite everyone etc and take care of RSVPs.
Then the night of have a group that you were going to meet up with have everything decorated and set up so when you walk in there’s someone to take pictures!