Gennaro is the legal counsel for InGen. Don't get him confused with the character in the movie: he's not the cowardly weasel he's made out to be there. Sure, in the book, he sometimes has to be persuaded to follow his better nature, but he does help out in some tight spots.
He also has scruples; he's not a stereotypical sleazy lawyer. While he wants the park to be safe, knowing that it could make a fortune, the visit quickly convinces him that Jurassic Park must actually be burned to the ground: it's not safe, and it never will be. It isn't worth the investment, no matter how rich it could make him.