To me a "gig" means a paid performance that is fully scripted and planned out. You know what routines you are going to do and in what order and exactly what you are going to say.
Think about if someone went to a play, arrived late and asked the actors "can you do that scene in the beginning over again so my friend can see it?" Or if you came late to a comedy show, and asked the comedian "can you tell the one about your mother-in-law again, my friend here said it was really funny."
What it sounds like is that you are doing tricks for people, without any structured order or presentation. I'm also guessing that you are probably in 9th or 10th grade, so you are not much older than the oldest kids you are performing for.
The answer to your question is that you have to establish a professional presence and maintain control at all time. Now this doesn't require you being rude ("Shut up kid, can't you see I'm doing something else?") but it doesn't mean you have to let the spectators control what you do (much like dealing with the spectator who askes to shuffle the deck).
If you are doing a show (rather than walk around), establish an area that is your stage and an area for the spectators to sit. This can be as simple as having chairs set up in a row for seating and performing in front of a table that has your props on it. That creates an imaginary "fourth wall" (this is a theatre concept denoting the separation between the actors and the audience). But unlike theatre, the fourth wall is able to be penetrated by the audience when YOU want it to be. This allows you to allow the audience to participate when you want them to.
For example, I had a young girl in a room of adults yell out with joy "it disappeared" when I was performing my egg bag routine and I showed the bag as being empty. Her mother looked mortified. I looked at her and smiled and said, "it disappeared." When the egg vanished for the second time, I said "she turned the bag inside out and the egg..." and then looked at the girl. She proudly said "disappeared!"
This allows you to ignore comments that don't increase the entertainment, but also to play up comments that make your show more entertainment.
I was presenting an effect where the presentation was about an effect that my Uncle Jim came up with that didn't work. I then told the audience that I would make the selected card disappear from a deck held by the spectator and appear in a bottle held by the another spectator. One member of the audience said, "that's impossible." I had her repeat what she said into a microphone and responded, "I know, that's what I'm thinking right now. I really hope this works." Later in the show, when I was giving a fake explanation (think like Copperfield's disappearing duck) she said "I don't believe it." I turned to her and delivered the next line in my script which was, "You're not buying any of this, are you?" And then transitioned, "Despite my appearing to have done absolutely nothing..."
Sometimes, you do need to ignore the audience. In kids shows, kids often blurt out "I know this one." It really doesn't matter if they do or not, they just like saying it. Normally, I just continue with the show, directing attention to another kid who is behaving well (sometimes rewarding the child that blurts out stuff causes you to lose control because more kids will follow the bad behavior). But there are always exceptions:
In one show, where the kids were up front and the adults were in the back, I started to do a card trick. I asked a kid to pick a card and the kid next to him said "I know this trick!" I decided to have some fun and pretended that I was really thrown off. I asked the kid, "are you sure?" Of course, the kid confidently said "Yes!" I then proceded to say, "In that case, let me do somthing different." I took the card back from the kid who chose it, gave the deck a shuffle, spread the cards and said, "Hopefully you don't know this one." I turned to the kid who originally selected a card and asked him, "Pick a card...." The adults in the room completely lost it laughing.
My response to a specific quesiton to do something again would be, "that was earlier in the show, I have some other things that I want to show everybody else." Or, based on my character, I'd say something like "Don't worry, that was just the warm-up, the rest of the show gets better." Giving in once, leads to them asking again. Really, the answer is just asserting control. As you can see in my examples, I always followed my order of effects and my script.
Finally, I'm curious why the other kids weren't watching the show. If this was something other than a typical show, then there may be other strategies.
