to be clear, my son makes a mess with any food. but, i specifically choose foods that don't crumble too much (muffins) or squish too much (bananas) or are sticky-wet (juices). home-made energy bars and dried fruit are our norm. i have water in a water bottle (metal with a sport-top) for drinking. these are easier to clean up.
and, i don't see how having more than one child needs to change these policies. older children simply eat more dried fruit than younger ones. *shrug*
Also, you'd be amazed at how finicky a four year old princess can be about what she will and won't eat.
Oh, and the baby has severe allergies *and* toddler preferences. Bananas are actually one of her few 'in' foods right now - and if she doesn't get to nibble in her seat, then all hell breaks loose. Same for the princess. The boys just get moody if they don't snack, or worse yet, their humor takes a dive into bathroom territory as they get the teenager-hasn't-eaten-in-the-last-45-minutes-giddiness.