Need Advice: roles for other party members in a single player contest

I’m doing a pokemon league-esque competition in my campaign, the party will likely be able to attend it in a session or two, there is only 1 player that has enough “pokemon” to compete in and I wanted to find some ways to incorporate the whole party so everyone can have a job or activity to do so it’s not just 1 player fighting a bunch of fights on his own. Has anyone had other “supporting” roles in single player contest/competitions that have worked well before?