if you are dropped off at 10:30, it will probably take the group a good 15 minutes to reach parry hotter.
gotta think about crowds and keeping your group of kids together.
did your school group go thru universal for the tickets?
group rate is possible with food vouchers.
if that is not the case, i would go for a counter service that has indoor and not outdoor seating so you can count noses.
if you are at the studio side, Louie's and IFFF have good choices.
both have seats inside and a restroom nearby.
IFFF has tv's with shows playing all day long.
if you eat at ioa, thunder terrace also has a nice set up inside and a good choice of food.
try for the rides that has the single rider line so you have less line waits.
save those long waits for the rides you must do such as forbidden journey.
yes, by all means.
a day in the park is much better than sitting in a classroom.
have the kids give you their cell numbers so if one lags behind or gets misplaced, you can call them.