Setting up Apple Watch SE Series 2 GPS for my 9year old

We’ve recently purchased an Apple Watch SE Series 2 GPS for our son and are trying to set it up using our family sharing account as he has no iPhone himself.

We are struggling to complete the set up process and are confused by the likes of cellular and if this is required/able to be switched on/or even necessary.

We simply want him to be able to use his watch for basic functions through the family sharing account but cannot find any definitive conclusion to the set up issues we are having. Any help is greatly appreciated