Whatever you do, talk to their parents (and them) about opening and starting their own IRA’s with 75% of whatever you pay them, preferably ROTH’s (50, 60-years from now they - and their heirs - will thank you like the bejeesus)!!!
WHAT??? Tell them you’ll only pay them by “direct deposit”? They want that jingle in their pocket. Depending on job I’d say $10-15/hr or better yet by the job.