A group of warmly dressed people in the back of a truck.
A children's group is in  a truck.
The group could be anyone, not necessarily a children's group.
exists e1 x1 x2 x3 x4.(n_back(x3) & a_topic(x1) & of(x1,x2) & in(x2,x3) & of(x3,x4) & n_truck(x4) & n_people(x2) & Theme(e1,x2) & v_dress(e1) & r_warmly(x2) & n_group(x1))
exists p1 x1 x2.(exists x3.(in(x2,x3) & n_truck(x3)) & n_group(x2) & of(x2,x1) & n_child(x1))