The moms precut the bottles and we gave the kids permanent markers (other kinds will just wipe off) and a variety of stickers to use. I cut my jugs the opposite way that the website said because I thought they would work more efficiently cut the opposite way.
The balls were even re-used. I once got a huge bag of balls from someone on Freecycle and kept out a small bag of about 20 balls and passed on the rest of the balls to my mom so she could have a ball pit for the grandkids. We used them for a ball pit for a couple weeks, but seriously, picking them all up was annoying, better to let grandma have them and let her pick them up infrequently then me having to pick them up every day.