Is your child starting pre-school in September? Maybe use this time now and the school holidays to get him trained.
I found pre school to be a help and a hindrance for my son.
In some ways, it was great as other children were using the toilet or potty so he could copy. But in other ways it threw him back as the pre school would go out for walks nearby and if my son needed to go, he would not hold it in.
Pre schools are great at encouraging children and expect little accidents and don't mind at all.
My son was trained at home when be started pre-school but not when he was there so had to put a pull up on him as he used to wee so much!
Pre school staff are very supportive and you can tell them everything about your sons existing toilet habits and what help he needs.