Panda Holding Experience - can you pre-book direct with park

Hi, we are in Chengdu late May 2016, and from what i can see the main Panda park in Chengdu currently does not offer the ability to hold the pandas, instead you need to go out to Dujiangyan Panda Base. Can you book online direct with Dujiangyan, or do you need to go on a pre-booked tour? How far in advance can you book? We do not have a lot of time so were looking to do a half day trip to Dujiangyan but also the next day spend some time at the main panda park back in Chengdu. Thanks!