It's been a year since I went (late April 2018), so take that for what it's worth, but for my 2 night stay, I was tempted but glad I didn't buy the Fastpasses. The reason was that I approached the park in parts by riding certain attractions the 1st day and by the 2nd day, I had done everything I wanted. At the time you could buy individual FPs instead of the set, and being the frugal guy (banker) that I am, I would have only bought a select few popular attractions instead and left out attractions lower wait attractions such as Pirates.
A little different for you with kids and on a wknd though. 1st day, because I arrived well after park open, I think in the early afternoon, there were limited free FPs available (something like Buzz only, which is usually one of the last still available). 2nd day, I think I went for Soaring FP, because it was the most popular attraction during my stay. I think going for Soaring FP, being so popular, made it difficult to have any choice on a second FP. In general, I think its unlike MK at WDW in that you can't expect to obtain much more than 2-3 free FPs, depending on your choice. The park is gaining popularity and wait times.
Many, not all, of the native Chinese, will sprint towards the most popular attraction, right by the CMs that barely put up any resistance (Soaring for my stay). It's important to be there early for rope drop, and get to as many attractions early. If I couldn't be anywhere near as fast as the runners, I think I'd try to FP the number 1 attraction as soon as I got in able on my app, whatever it is now, and head to 2nd or 3rd choice first instead or go in the opposite direction and plan on doing a select few missed attractions just before park closes when wait times fall.