Maybe one of these is suitable.... (they are in the Installed English Extras>templates...)
Time Billing and Time Cards are worth a look.
I assume (just to be clear) by "check" you are meaning what we spell "cheque" in non-US English. Perhaps Expense Report is ok as a starting point. One of the other templates for Payroll might also be useful for this...
I started out as a special ed teacher. Depending on the range of disabilities you are dealing with, I imagine that you might be best building something from scratch with absolute simplicity to the interface using a table format or a controlled single record view. Then perhaps introduce more complex layouts as they progressively learn each skill... and vary the designs and icons to generalise and maintain the learning.
You might also find that entry via iPad could be a good skill for the future... as well as a device more easily used by those with Downes Syndrome or Cerebral Palsy.
I taught a young man to use a blowing-tube-cursor connected to Apple IIe with adaptive firmware to edit our school magazine MANY years ago. I also made pictorial interactive cookbooks using Hypercard... you know... there are 2 eggs so you get 2 eggs and then click on each egg and it disappears then shows the next ingredient to get... that sort of thing. Technology has come a LONG way since then... I'd love to know how you get on...