Kid shots with FA77/1.8

The image quality of FA77 is very good, giving very pleasure result. However, the focus speed on my istD is quite slow, and cannot lock into correct focus quite often. It's a big problem with kid's shot, so I have to resolve to use MF. Although the f/1.8 make it very easy to MF, I still hope the AF speed problem can be solved in other DSLR models.