We've been disappointed with CM the last 3 times we've gone, both the food quality and the character interaction.
WE love love love O'hana's-- your 8yr old and maybe the 10yr old will enjoy the games--my 13 yr old still likes to get out there and hula hoop!
Don't eat anything like all day, though, you'll be offered a TON!
Unless I had real little kids, I'd go with O'Hana's hands down!
Have a great time!