Given the choice of too dressy or not dressy enough I always go with too dressy.
I think wingtips would be fine. If the dress mode is very casual I would avoid shoes with a mirror shine.
That's generally where I've been erring too. It's far better to be overdressed than underdressed in most situations. I still really suggest he look into a quality pair of wingtips. Dark jeans and brown wingtips actually looks pretty great in a casual setting, and not "stuffy" or "dressy" at all. At the same time, they can be worn with blazers and suits as well. Very versatile. Boat shoes, on the other hand, are pretty casual and best reserved for wearing either with jeans or shorts.