i agree with sharnita. 3 year olds are learning the concept of 'mine'. i have a 15month old and he knows what's his. i also agree with jedikaiti. FIL is playing by his own rules.
if he gifts it to her, and the parents allow her to open it but use it as a family item, the parents may run into the problem of FIL consistently referring to the gift as belonging to the 3 year old. that's going to cause some confusion.
and i may be jaded here (i've worked clinically with youth who end up in group homes with significant entitlement issues), but i, too, wouldn't allow my child to have such an expensive 'toy' at a young age. it's not something i can rationally argue, but in my mind it sets an unrealistic precident. FIL gifts an ipad today, maybe next year it's something more expensive. it starts to create a divide between the parents and in-laws. 'no, 6year old sally, you can't have a phone.' 'then maybe grandpa will get it for me.' i'm for setting limits and getting him on board with giving it to the family while DD opens the 'family gift'. he'll still get to see how excited she is, but won't cause needless triangulation.