The Feast of Ravenmoor has a local festival, and Murder's Mark takes place at a sort of carnival.
It really depends on how you want to run the adventure. If it's casual, you can just take a bunch of normal festival games and assign skill/ability checks, then see how many the players can win (aim for them succeeding at, oh, 2/3rds or so of the challenges, without using special magical buffs or anything).
Truth is, though, if the festival is being held in their honor, they probably wouldn't be entering a tournament themselves or anything - it's more likely that the locals would have a tournament for OTHERS, with the victor getting the right to challenge one of the PCs in single-combat. If your players enjoy a little bit of friendly PvP, you can ask them to make 2-3 new characters (or hand out some balanced ones you made) and allow them to play those going through the tournament, and whoever wins can duel one of the party members.
Otherwise, mmm, just try to let them have fun. XD
