Ouch!

Tell your friends to level together in the conventional way while you focus on leveling your own team - that's painful enough anyway.

No way on God's green earth is it going to be fun to do things the way you are. I struggle to motivate myself enough to boost my own characters, let alone other peoples!

Apart from anything else, they'll end up at the level you're all aiming for before your team is! If you really want to help them, it probably ought to be when you've achieved your goal and want to help them catch up by nuking quests, etc, for them.

If it ain't fun, you need to stop doing it.