As a previous aide in an intermediate special educational department, what really worked for us was having a lot of textured napping materials and mats. We had a few sleeping bags and some bean bags. Also some character blankets that were donated to us were a treat because one particular student LOVED Star Wars - so he got the blanket with Star Wars on it every rest period. I also had a few quiet games (games made with just Velcro and laminated paper) for my busy students. Sorting tiny erasers with little prongs or even a piece of paper with stickers they could do to work fine motor skills. Also, have you tried a naptime song/video. There are wonderful videos on YouTube with just soft music and puppies running through the grass. So soothing and SO relaxing.