GPS for vulnerable child

Hi All

I'm new here, but looking for advise please. 

My son is 5 years old and non-verbal. He was diagnosed at 3 years 8 months. He started a specialist school in September, about 20 miles from home. He gets picked up each morning by the bus (which he loves) at around 8am and is dropped off anywhere from 4 to 430.

I would like to buy a GPS tracker so that I can keep an eye on his journey home, I like to have his dinner ready as soon as he's home otherwise he won't eat and because of traffic and the journey home is quite far, his home time always varies. If I can see roughly where he is I'll be able to get his dinner ready. I've spoken to his school and they're fine with it.

Does anyone have any suggestions please? Seems all the ones I look at have a subscription fee. I bought the Samsung tag 2 but it only works up to 120m