Potty training

I waited till all of ours were able to hold a sensible conversation, and the whole business was done in a couple of days. They were all well over two years old.

I do agree with PP. Every other weekend is not enough and could delay the child further. Before starting we spoke to my daughters childminder and nursery and they were both very happy to help. They felt with accidents and continued to encourage my daughter when in their care.
If you start and then parents stop he could turn against the idea.

I used to put mine on a potty in the bathroom or cloakroom about 60-90 minutes after a meal (when they were about 12 months) and I'd sit on the toilet seat and read a story to them.
They got so involved with the stories that 'going' just happened without needing encouragement.
I can't remember doing charts or giving treats, just 'Good boy/girl' and 'Shall we wash our hands then we can go out/play?' Whatever, it worked and took only a couple of weeks before they started handing me a book to read.
I echo some other comments which suggest the parents agreeing to your plans.

There are stickers that go down the toilet and change colour when 'warm' liquid hits them. Certainly improves the aim of little and big boys ???

I agree you have to wait until they are ready. One of my grandchildren was 3 before ready and still then had accidents for a while the other was ready at 2 and 7 months and decided himself he didn't want to wear nappies anymore and didn't have any accidents . Is he aware when he is weeing or pooing?

I personally feel this little boy is a bit young unless he is showing sure signs that he is ready. I wonder how the timer is to be used? Generally children let you know when they are ready and then the whole process is so much easier.

I despaired of my DGD being potty trained then one day she declaired she was finished with nappies and was dry night and day ever since . If you will not bw there all the time to continue this regime I think you will be frustrated.