Probably already figured it out but I had a similar issue. What I did was I piggybacked off of a "player present" trigger to disable the other spawn points until they got to that point.
More specifically, the players start in a helicopter so there's a respawn point there. I also had respawn points in two vehicles they would be using in the mission. The first task of the mission was to get to the vehicles (halo jump). Once they got to the vehicles it would complete the task (player present trigger around the vehicles linked to set task state module "succeed"). I also synced that same player present trigger to the two respawn modules for the vehicles. That way the vehicle respawn points wouldn't activate until the players got there. They could still respawn at the chopper but they'd be left behind without a ride so it's their fault for not paying attention.