I don't think there has to be anything problematic with fertility gods, unless you're just focusing on the sex aspect that some of them have but in that case it isn't the god which is problematic it's probably the players.
Other fertility gods covered childbirth, motherhood, the ability to have many children non of which is problematic. They also covered crops, Thor is a fertility god in this aspect since he brings rain.
There's no reason to have statues of a Priapus analogue in your game if you think it's an issue (although, ring toss...), and maybe don't add in temple prostitutes if you don't think your players will be able to handle it. I think a lot of this would be so far in the background of a campaign setting anyway that it probably wouldn't really come up unless the DM specifically notes the statues of Priapus lining the street, parts of which have been knocked off.