Transit Visa or Transit Permit necessary for 6 day transit stay in Shanghai?

I'm a Belgian citizen living in Japan (valid 5 year Japanese Residence Permit + valid Belgian Passport). I will travel home to Belgium for summer holidays with my 13 yr old son around mid June. We will travel to Brussels via Shanghai and want to take 5 or 6 days to visit the city. If we have confirmed onward flights to Brussels and we don't stay longer than 6 days, do we need a Transit G type or Transit Permit? If yes, do we need to obtain that from the Chinese Embassy in Tokyo or can we just get it at the border when we enter China? How much will it cost? Thank you for your help. IG