It depend on what stage any one of them is.
Some may never be edible.The ripening, does not require sunlight. Because fruits do not interact with light and air. Now that the vines are dead, the rest of ripening is an internal process.
I would say keep them in garage rather than in greenhouse.

Watermelons won't get better after harvest. It's all downhill from here. So cut them open and see if they are edible, not all at once of course.

Thanks for the help. I cut one open and it was still white inside. Maybe I'll have better luck next year.

not sure if you have tasted the white one, but last year I picked a sugarbaby that I thought was ripe, but was still white. I tasted it anyway, and to my surprise, it was sweet... not quite as sweet as a full ripe red one, but it was definelty edible..