You could use your digital camera (if you have one) to take a picture of the layout, or a picture of each row as it is arranged,
then pick up everything and refer to your pictures.

My approach is similar to yours. I cannot live with two greens or two blues sitting right next to each other. It does take longer, but I am completely satisfied with the final quilt. You have to work in a way that will make you happy.

I use a large piece of felted type material as a design wall, whether it hangs or lays on the floor. I roll it up on a large cardboard cylinder like upholstery fabric comes on. Lots of either paper scraps pinned to the pieces, or masking tape to keep everything in order once it's off the wall.

I need to arrange my scrappies to be happy with the fabric placement. I use several of the above suggestions.
- fabrics are placed on a flannel design wall in what I think is a pleasing placement
- I snap a digital photo and make notes on it in Paint regarding what should get moved where. For some reason, I catch a lot of mistakes by snapping a photo that I miss when looking at it with my eyes in person.
- once I am happy with final placements, I roll up the design wall and carry it to my machine
- I unroll the flannel one row at a time for construction
- if it is a quilt assembled by rows I sew a piece of paper with the row number onto the first block in the row. That not only keeps me straight on which row is what but it also helps keep the row from being turned upside down. And, no pins are in my way. I use a long stitch so the thread is easy to remove when I no longer want the paper marking the rows.

Your son's floor will be unusable until the design wall is rolled up. Or, as Cedar mentioned, can the design decisions be made with a design wall pinned to window curtains that are a big enough size?

I'm going to be of no help here because I LOVE CHAOS and there's always a little order hidden in chaos. I usually go full-out random and do very little editing.

I do try to make sure two IDENTICAL pieces aren't touching but that's about it. 2 different red prints are fine touching for me, but 2 identical red prints touching is something I try to avoid. But if it happens between rows I don't worry about it.

I do coin stack style scrappy quilts and I put together my rows and then play with arranging the rows to get a good distribution. Sometimes one area of the quilt ends up heavy with one color but I'm ok with that. If I threw those pieces into the air there's a good chance some similar pieces would be touching so if that's how Nature does it, I'm OK copying that. :)

I have a hard time with scrappy. My scrappy ends up being very planned scrappy which is probably not really the definition of scrappy. I'm doing "scrappy" with 2.5" squares as leaders and enders and not paying any attention to what is going with what, other than not putting two of the same color together. So that project will end up truly scrappy.

I'm more of a grab and sew when it comes to scrappy. I may not put two darks or two lights together if they are big pieces but other then that, it's scrappy.

I've done four quilts that can be categorized as scrappy and I just placed everything as randomly as I could. I had a blast making them.

I have space issues also so I do as quiltzstring suggested- I get piece of paper or graph paper and mark out the color layout. works great when yodon't have room or can't get on the floor as I can't do either! Havent had any issues other than misplacing my paper! Good luck! :-) would love to do that pattern but intimidates me!! If you have easy short cuts would love a pm and hear them ! :-)

I do what was posted earlier.. I lay everything out and play around with them until I like it. (my living room is my only good floor space). Then I take several pictures. As I stack them up I pin them with a piece of paper with what row it is. Then I sew the row and pin the row label paper back on the strip. I have the picture on my computer screen for easy reference. Good luck