EB Ceremony Start Time question

[Jojoya]

Please pardon my paranoia but this is one thing you don't want to mess up, right?

I have some friends who may not make it home from work right at the start of the ceremony my friend and I are having. Given what the "rules" say about entering the chapel and starting the ceremony, am I correct in assuming that...

1. if our time slot starts at 5:00 PM...
2. ... my partner and I need to be in the chapel before 5:20 pm...
3. ... but can start as late as 5:40 pm ...
4. ... so we can tell our guests that the ceremony starts at 5:30 pm ...
5. ... and as long as they enter the chapel before we start they're fine.

That should work, right? It makes sense to me, but my main concern is the thing about the guests and whether they can show up after x:20 and still get in if the ceremony has not yet begun.

Thanks in advance!

If you talk to Etoinille at the Sanctum, she says "Assuming that the ceremony is still in progress, guests may arrive at any time."