Transport around in Sichuan

Hi
My parents and I are in China in September. We are just trying to plan our time in Sichuan.
We've booked to arrive at Jiuzhaigou Airport at 1645 and we were planning to go straight to Jiuzhaigou National park for 3 nights. However I was now thinking it would be good to see Songpan and Hualong National Park if we can in this visit.
My question is if we stayed the first night in Songpan and then the next day went and looked at Hualong National Park would be able to catch a bus up to Jiuzhaigou that afternoon? We would then have two nights (one full day) in Jiuzhaigou to explore the park and then catch the bus to Chengdu.
Also can we book the bus to Chengdu in advance?
Many thanks

Hazel