N.C.
Hi,
$10 an hour is fair - but not PER KID!! I give my sitters $10 and hour for BOTH of my kids (ages 4 and 7), so our total would be half of what you paid! I think that $20 is way too much and there's plenty of sitters out there who will watch your kids for that. (I'm assuming you don't live in SF, which a sitter might be expecting more)
Good luck!
Nicole