You posted in the official support forum where the community can’t respond. The regular skyrise subforum would probably be the best place for community input, and the official Q&A is where Karthik answers.
Karthik has said in the past that wireless communication like what you described is not legal during a match, so your drive team members can’t use it. However, I don’t think there are any restrictions on wireless communication in the rest of the expo center, and I know teams have used walkie-talkies at other events.
To add to the info - make sure your wireless communications do not interfere in any way with the 802.11 frequencies the robots use. Would be a shame to have robots stall because someone wanted tacos