Just be careful with the thin superglue. It's has almost no surface tension, has very low viscosity and so runs everywhere, so I'd mask off all around the crack to minimise the sanding you'll need to do. Ideally you should get a needle-nose applicator for it so you can put it right in the crack.

Also if you are planning on staining the guitar, I'm pretty sure that the superglue won't take up any stain, so you really don't want to get it on the surface of the body.

Can you get a thin knife blade or a thin needle down the crack to see how deep it is? If its only a mm or so, then it's probably not worth worrying about and just fill it with timbermate. If it's deeper, then it will need some glue, but I'd also try to then clamp it as tight as possible to seal up the gap. This will tend to squeeze out any glue, so don't use too much and I'd probably use PVA rather than superglue as at least you can clean it off the surface with Goof-Off. I'd put cling-film between the body and the wood you'll use to help clamp it with so that the clamping wood doesn't get stuck as well!