Can't say I've seen a kid that hasn't liked the swag, most of the kids I've been around have been dying to come on a camping trip and since the adults and older kids used swags that was what they wanted to use as well. All country kids though, not city slickers, I suppose that would make a difference.
The backyard camp sounds like the way to go, try and get a few kids around his age that are comfortable in a swag around for it as well. "Peer Pressure" can work wonders in getting most kids to try new things. Not suitable for some children of course as they all have different motivations, temperaments and such.