I think it might be possible but quite tight.
7:10 flight would mean boarding start around 6:30. Taxi to the airport would be around 45min-60min so leaving the tour at 5PM gives you only a bit of leeway to find a taxi, account for traffic and immigration.
One alternative option is to take the subway from Zhujiang New Town, around 50 min to the airport but no worries about traffic. Plus the price at less than 10RMB is a bonus compared to taxi fare (120-150RMB)