So after a lot of thought, I came up with an idea to sew a dust ruffle in a way that it shouldn't slide and to just use a colored fitted sheet on the bed when no one sleeping.
I moved the top mattress and covered the bottom box spring with an old fitted sheet and pulled it so it was tight.
Then with a yard stick and marker, I marked a line 3 inches inside. It will be my sewing line.
This way the dust ruffle is completely under the top mattress with no poking out of the base sheet the dust ruffle is sewn to.
Then I looked through my fabric stash (I have a big fabric stash, most of it was gifted to me).
My original idea was to reuse some floral curtains but I can't find them (maybe they were too faded and I got rid of them, who knows?). So I decided to use a fabric that the children would like.
I had long lengths of some mountain wildlife fabric and some deer fabric.
I went with the wildlife print. Then I measured the length - I think it was 18 1/2 inches, allowing for hem and turning under top.
I cut out lengths and I used either 5 or 6. I sewed them all together in to one very long length and machine hemmed the bottom and turned under the top edge about a 1/2 inch.
Then, I got down on my knees and pinned the dust ruffle to the fitted sheet base all around 3 sides. I pinned it on the line I drew.
I took the whole pinned together sheet and dust ruffle to the sewing machine and sewed it close to the pinned edge. This was the trickiest part as it was a rather big piece to steer through a sewing machine.
I put the freshly sewn dust ruffle back on the bed, put the mattress back on with a sage green fitted sheet and added some patchwork pillows I sewed about 6 years ago.
Also, I know the top sheet will need laundered often and it will be much easier to wash than a bedspread or quilt.
The bed is ready for anyone to sleep in it, We can just add the top sheet and blankets.
I like that the dust ruffle hides the ugly metal frame and I think the grands will do some pretend playing with the animals and cabins on this dust ruffle.