Should I let my plants keep flowering or harvest and leave them if I need to travel?

Harvest as late as possible and slow dry while you are away. I would not leave them unattended for 10 days and it is better to harvest a bit earlier than harvesting over ripe buds that have been left too long.

I gotta say, I would never leave my plants and go off for 10 days even if a friend is going to "help" tend them... friends don't know what the hell they're doing even if you explain it to them - and the plants won't survive 10 days left on their own even if you're growing hydroponically.... I would chop at the very last minute and hang the whole plant to dry slowly while you're gone. You'll have to hope it's at the right stage of ripeness when you do... Good luck!