We are planning our vacations/family visits in europe and asia and I need to decide between booking with miles 2 C seats (flat ones most likely) and 4 Y for 2 adults and 2 infants. Total mileage amounts needed are very similar and I'll have an option to use either BD or BA miles to avoid 10% full fare surcharge so taxes and fees are not dramatically different.

I think a bed in C can accommodate 1+1 for sleeping and provide some playing space, on the other hand a car seat in a separate seat in Y is probably a good option too.
Any thoughts on what to pick?