The fact that he's a civilian isn't a bad thing, just means it's a little harder to get him to go to the island. Could even be a little more interesting to see him getting in way over his head.
Maybe he'd go for some kind of personal reason? In your bio for Karl, I think you mentioned his family often has dino parties? A reason
could be that one of the dinos attending one of their parties (maybe even an uncle, something like that) was going on about an island, mentioning some dodgy stuff about it which sounds similar to what Circe is talking about? I dunno, nobody can accuse me of having good ideas
And I'd be happy for you to join Rocky, but like Ducky said the actual decision is with Pterano.