We’ve had this exact scenario happen to us twice at graduation and I don’t have a solution yet. Robot tested in the venue with no problems whatsoever, excellent communication over 150 ft range. As soon as 800 or so people show up, we’re dropping packets like crazy and can barely even operate the thing, even at closer (<50ft) range. Operating direct from the Classmate PC.
As others have said. Use the 5g band. Use an encrypted SSID to keep the curious from connecting. Remember that you will have to set one of your routers to bridge mode (assuming your computer doesn’t have a 5g radio).
We use the one of the old brown bridges from breakaway plugged into the lap top with the AP on the robot.
I’ve seen this problem at demos and off-seasons. Yes, you definitely need to switch over to the 5ghz band, it’ll be a lot less crowded. At 2.4ghz you have to contend with most school wifi, almost all cell phone mobile hotspots.