Our grandson is now 10 months old and stays with us every Friday. She is anxious to start the training process with him. She searched high and low for a potty chair with a tray but none were to be found. She perused the internet with no luck. She lamented to me and I off-handedly said I could probably make one. This got her excited BUT I would have to make two; one for us and one for our son.
This shows what I wound up with. The potty was actually pruchased and I built the potty stand WITH tray to satisfy my wife. She is very happy with the results and can't wait for our grandson to get here on Friday so she can test it out.

This picture shows both chairs completed and sitting on my workbench. The frame and tray are maple made with some short pieces I had laying around. I didn't have enough maple for the platform that the potty sits on so that is made from generic whitewood I had laying around.

This shows a head on view of a single chair. The tray pieces had a nice curly grain pattern. I routed the tray recess with my newly purchased OPR. I had to make a special OPR pin to match the 1 1/4" tray bit I used.

This shows the pieces for the tray locking mechanism. I could have purchased a metal tray mechanism but decided to make my own instead.

This is the tray lock attached to the underside of the tray. It works well and holds the tray securely.
I earned a few wifey points on this project and now I'll have to figure out best to cash them in.