Two children are on a fairground ride.
children are at the fair
Two children can be referred to as children and fairground ride implies they are at a fair.
exists p1 x1.(exists s1 x2.(on(x1,x2) & n_ride(x2) & a_fairground(s1) & Theme(s1,x2)) & n_child(x1) & card_eq_2(x1))
exists p1 x1 x2.(n_fair(x2) & at(x1,x2) & n_child(x1))