When you have 2 people that are about to go into this journey, is it a good idea for the person who goes first facilitate for the person who goes second?

Do you mean - "will I be able to tripsit 2nd one after my comedown?"

Sure, I'd say it is a great idea, because you can better relate to whatever is going on with your subject. Though you should give it at least 5-10 minutes after your come down, to be able to grasp reality better, you might have a big urge to talk or discuss whatever happened.

For me best tripsitter during freebase trip is the one that fits following criteria:

1) Takes your smoking apparatus from your hand if needed and makes sure that you are comfortable
2) Knows when to shut up, sit/lay still for a while and not make a noise and when to talk
3) Knows how to comfort you, if your trip goes slightly off the rails and you meet exponentially fractal octopus of doom that tries to convert you and teach you secrets of dark blood magic