Two guys and a girl smiling.
Several people are unhappy.
Sentence 1 is grammatically incorrect: Two guys and a girl ARE smiling. two guys and a girl totals three people, not several. They are also smiling, which would indicate that that are not unhappy.
exists e1 s1 x1 x2 x3.(a_topic(s1) & subset_of(x2,s1) & Actor(e1,x3) & v_smile(e1) & (x2 = x3) & n_girl(x2) & subset_of(x1,s1) & n_guy(x1) & card_eq_2(x1))
exists s1 s2 x1.(Theme(s2,x1) & a_unhappy(s2) & n_people(x1) & a_several(s1) & Theme(s1,x1))