A windshield would be necessary if it is a windy day. Otherwise the shures should be alright, but the studio mic should probably use a windscreen.

Some basic tips would be not to keep the mics too close to any of the kids. Otherwise some will stand out more than others. Two feet would probably do it. Space out the mics a bit -- keeping them close to each other will cancel some of your sound. You shouldn't need more than two or three altogether besides the solo mic.

Chony