hi, where I can buy tickets for the sighseeing bus in Shanghai, I will go there in 4-10-14 with my son

The tickets can be bought at bus driver and any of the local sightseeing bus station.
The starting station of line 1 is at SH Urban Planning Exhibition Center (People's Avenue) and you can buy ticket there.
Or if you can tell me where you plan to stay when you were in the city, I may help you to find a close ticket office for you.