These were common when I was a kid. We even had 'em to play with at school (kids circle it, move it up and down until it inflates and run under it). Makeshift tent and sunshade is a good idea, seen 'em used for that. These were the old real silk ones too. In the army, they were used for shades at ranges sometimes.
I don't know what they're worth. I have a radar dispersing camo net though that I got that I use for the same thing --turns out the damn thing is worth $1000!
Only problem with the chutes is that they are so thin they get torn up easy, otherwise they'd be good for laying out on the ground too.
You could also cut 'em up and make MC Hammer pants. You know, bring it back.