One of the most common concerns for parents is that their child's legs are bent and appear uncomfortable against the seatback, and in that position are at a higher risk for injury in a crash.
First, children are far more flexible than we are and most likely aren't uncomfortable in this position. Second, crash data shows that lower-extremity injuries (such as those to the legs) are rare for children who ride rear-facing and are as likely to happen rear facing as forward-facing. Riding forward-facing does increase the risk of head and spinal injuries however, which are far more serious than a broken leg.
Regardless of your child's orientation, passing a snack is a risky move, because drivers tend to turn the steering wheel when they're reaching, which could lead to an accident. Eating in the car is not a 'best practice' in general, since being secured in a separate seat delays your ability to respond, should there be any choking, spilling, etc. Allow time for snacking before you head out, or plan a few minutes to stop during your trip for a bite or drink.
Though parents may be eager to graduate their children to the next step to mark their growth (and potentially to make things easier for themselves), the fact is that each step forward to the next type of child restraint actually marks a step down in terms of overall safety for the child. For example, for children who could potentially ride either way based on their height, age and weight, forward-facing is less safe overall than rear-facing. Similarly, for slightly older children, using a booster seat is less safe than a forward-facing harness. Be consistent and don't make exceptions—such as "I'll let him sit forward-facing in Grandma's car"—and children are less likely to object.