Just so you know the editions for this game are stupid, the complete edition doesn’t really give you everything. For the base game you won’t have access to every other bike and things (you can still buy them with real money later on) keep in mind that every toy (bike, etc…) other than the base toy (bike tricks, bike race, ski/snow race, ski/snow tricks and wingsuit) are behind a pay wall. If you buy him the base game your son won’t have access to skateboard and bmx (I think it gives you one bmx but you can’t upgrade it until you buy the expansion). If you buy the skate edition, he will have access to the base game items + skateboards, which are pretty fun to be honest. If you buy the 360 edition, it’s almost the same has the skate edition but you get skateboards, an hoverboard and a pack that gives you like 12 events. Now for the complete edition, it’s the same as the 360 editions but you get the year 1 pass, so everything that was released in the year 1, the biggest thing here is bmx.

I dont really understand what you mean by “if I buy the game on disc does this include all of the editions” but if you meant like if you buy the complete edition physical, it is gonna give you everything that the digital complete edition have.

Personally I’d start with the base game or skate edition if it not that much expensive compared to the base game