If done correctly by an experienced injector then you should be able to maintain all of your natural facial expressions after Botox treatment. In the crow's feet area, after your treatment you will still be able to smile and squint, only when you do you will notice a dramatic decrease in the amount of wrinkles in the area. Botox works great for the crow's feet areas and people are normally extremely happy with their results. Hope this helps!
With an experienced injector, getting Botox should most definitely not change the look of your face or make you unable to squint.