A couple of thoughts about fun:
1. If you have to ask "are you having fun?" the answer is probably no. Furthermore, you're probably making things worse by calling out the fact that there is fun to be had, and someone is not having it.
2. For some reason we keep up this charade that now we're at a fun thing, now we're not; while you're at a fun thing you should be having fun, and while you're not you shouldn't. (it's okay if you do. it's just unexpected.)
3. It seems very rationalist or logical or objectivist or WASPy or Cartesian or something (someone fill in the right word please) to treat fun in this way. We treat fun like an object that you can buy with a certain amount of time and money. When I put it like that, it's obviously nonsense. And yet, we patronize so many Disneylands that pretend they can give us exactly this trade.
4. An analogy: if life is food, fun is sweetness. A well-made meal will offer you sometimes a good deal of sweetness. But if you go looking for sweetness, you'll just be eating spoonfuls of sugar, and that makes you sick. (and doesn't really taste that good.) I guess what I'm saying is, if you have to try to have fun, maybe you should rethink your approach.