I agree with all said above
My experince running Tagcon is It is so hard to determine who will really show up

The best way is to make a firm pre-payment policy, say $10 at least 2 week in advance
that will eliminate a lot of maybe people.

waive the $10 for people who are bring necessary items as you know they will be there.

Next is delegation of duties (to unpaid volunteers)
most people show up to play and not to run an event, but if divided well, everyone will have more "Tag" time and less "lag" time.

As the person running the tag games and larp, I want to play too, but then there is the accusation of you did well because you designed the game. I solved that at TAGCON by having my character switch teams mid game or between games or having an "Opposite/equalizer" on the other team. In that case it was John Haugland and it worked very well.

David is right on the organization
1 game master
1 team leader on each side with all the info
Team leader delegates to 2 "sargents" to help keep his team organized/informed/quiet at instruction time and to the start up location quickly so we can get to playing.
Once again this is the set up I had at tagcon and it worked well for very complicated games.

Game master gets details to team leaders 1 week before event and reviews questions on game day
Team leaders the teach sargents what they need to know.
sargents and team leader then tell their team right before the game in a 5-10 minute session, then go play.

Before lunch play some LTTO games, zone, kings, hide and seek, etc

Starting after lunch each game lasts 30-60 minutes
with 10 minutes for instructions, rest

Game 1 - one life, simple elimination
Game 2 - respawn x1 at base only and 1 objective
Game 3 - respawn multiple at many sites, 2 or 3 objectives, special weapons
Game 4-6 add objectives, special weapons and characters with hidden agendas

At dinner have awards and prize give away based on points earned

evening games replay the games we liked best, but now at night and maybe a few new twists

Peter

And one minor thing, that might help speed up the complex games at set-up time: I would call what we played at TagFest a SCENARIO game rather than a LARP game, as there were really no characters per se, just a couple of players with specific jobs to perform.

So it seems to me that there is very little need for a back story -- it can simply be stated "Your goals are to ______ (fill in the blanks). The other team will be trying to _______ (fill in their major objective), and also trying to accomplish a couple of goals that you don't know about, but need to try to figure out and stop them. They will be doing the same to you. Now let's get it on!"

Is it possible to have Saturday as the adult day and all Sunday as an "open to public" day?

My schedule is quite flexible but I know a lot of my friends would have a hard time coming to an all day Friday event.

Just two more cents.