Jenie: Sorry it took so long to get back to you with the information about the dividing wheel.
The one that I have is older as it only will divide a cake up to 18" with 3 to 12 marking points.
You can make you own by taking a large round cake board, at least 19" across, put a nail in the absolute center with the tip pointing up. Then you will need round cake boards of different sizes, such as 4", 6", 8", 10", 12", 14", 16", and 18". Place the absolute center of each one on top of the nail one at a time starting with the smallest and mark the complete circle of the board on your wheel. At this point you should take the smallest and largest board and place evenly spaced marks on the board for a cake that would have three marks on it, you can use a different color for each new marking set and mark for a cake that would have 4 to 12 markings each. Now place the smallest board back on top of the nails and transfer your markings to your wheel. Then do the same with the largest board. At this point you can take a ruler out of one of the kids new backpacks and connect your color coded marks across the cake rings. Be sure to mark on the almost edge of the wheel how many markings this line will represent.
Now you have your own homemade dividing wheel. Here is a picture of the Wilton cake dividing wheel so you have a guide to go by.
Hope this helps!