They should have him be just a disembodied voice.
( They ( ( should ( have ( him ( be ( just ( a ( disembodied voice ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (MD should) (VP (VB have) (S (NP (PRP him)) (VP (VB be) (NP (RB just) (DT a) (JJ disembodied) (NN voice)))))) (. .)))
To be more effective with children, he should never be seen.
( ( To ( be ( more ( effective ( with children ) ) ) ) ) ( , ( he ( ( ( should never ) ( be seen ) ) . ) ) ) )
(ROOT (S (S (VP (TO To) (VP (VB be) (ADJP (RBR more) (JJ effective) (PP (IN with) (NP (NNS children))))))) (, ,) (NP (PRP he)) (VP (MD should) (ADVP (RB never)) (VP (VB be) (VP (VBN seen)))) (. .)))