first public performance this Sunday - ? what to expect?

Well, the group I have been jamming together with for a few months is playing at the church picnic this Sunday afternoon. This is our first public performance where we are playing to be entertaining, as opposed to playing old time gospel in a church service. Is there a difference? Yes I think there is. Perhaps a congregation is more forgiving of mistakes made? The performance in the services is meant to be the worship, and it's not about how good we are as musicians, per se (but at the same time you don't want to be too rough as that is distracting). Does that make sense?

But now there is this public performance outside late afternoon. We are the entertainment and I don't know what to expect. That sounds a bit silly, I know but as the days are getting closer I am getting nervous. We have thought through things like mosquito repellant and clips to hold sheet music in place on the stands. We are not off the sheet music, but using the music standsis I suppose a crutch, but I don't think it matters. Obviously you look more polished if everyone has memorized their parts, but I hope that won't be counted against us. We are doing 11 songs, broken into 2 short sets with another musician in between, so there's a little break to get water etc. We plan to get there early of course to set up and have everything right, including tuning! What have I forgotten? I have invited friends and coworkers - I don't know who will show up, but I do hope it's not too shabby as I have to face the coworkers next week..

So how is a person expected to feel/prepare? And does my observation about playing to be entertaining vs playing in a church service make sense?