I get it, he's your uncle and you want to trust the guy. And I'm not saying you shouldn't trust him. But if he's an elder and the elders want to meet up he's acting on their behalf unless you know otherwise. I wouldn't do it, but I get why you might.
If you choose to I would do what some other posters suggested: don't be direct with your criticisms, come across as weak, confused, that kind of thing, or even just play the I'm busy I'm depressed card. Do you know about the 'loyalty question'? One of the other posters mentioned it. If he asks you, Do you believe that Jehovah is using the faithful slave to lead this organization, or something like that, he's giving you enough rope to hang yourself by seeing if you'll out yourself as an apostate. Don't answer honestly.
The other thing to keep in mind is that with the two witness rule I think if you tell your uncle you don't believe in God, and then you tell somebody else that and both come forward a Judicial committee has the two witnesses they need to disfellowship you. Can any posters confirm that?