Two children are on a fairground ride.
parents are with their children
Just because children are on a fairground ride doesn't imply they are without parents.
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.(with(x1,x2) & n_child(x2) & of(x2,x1) & n_thing(x1) & n_parent(x1))