Good question @kmoody. Been looking around and nothing specific jumps out to track individual student . One idea I thought would be interesting is assigning one page per student in that group? So that they document what they are doing to contribute? But if their ability to edit each other's page is a challenge then just assign one Google Doc for each kid and embed them on these pages? That way while the group can see each other's single contributions there is better balance in ensuring everyone is participating equally?
Just my $0.02.