Ticket registration

I’m running my first race in September and I have a friend that is interested in joining me but he isn’t sure if it’s going to conflict with a hunting trip. I haven’t registered the tickets yet to avoid transfer fee later if he does decide to come with me. How much time do I have to register the tickets? What are the repercussions of registering late? Does it just mean I’ll have a later start time( tickets are for a 12pm to 3pm start time)? If so is that a bad thing? I feel like there is probably more traffic at obstacles later in the race.

Thanks!