My suggestion is to start playing up the idea that different people have different interests. Uncle Bob loves studying and growing orchids, Grandma loves to travel, Sally loves jazz, etc. It is normal that people have passions and they don't necessarily have people to share those passions with.
One thing I've noticed happens sometimes with families is that kids get a mistaken impression from parents. Of course nice parents go out of their way to indulge interests and it is great that you can take him to visit lighthouses. But, at the same time the reality is that this is an unusual interest not just for a five year old but in general and just because mom and dad are nice to indulge it doesn't mean that other kids, gifted or not, will care about it. It is great to have unusual interests, but that doesn't mean other people will share them. So, my suggestion would be to talk about the uniqueness of different people's interests and if he's interested also encourage some discussion about more general interests that he can share with his same age peer group as well.
