We went in 2015 with a voracious 19-month-old and free dining, and it worked out great. There were 3 adults and one kid, plus the infant, so we all just shared a bit, and it left us more room to use our snack credits later! We only ended up doing one all-you-can eat (Ohana), where each kid must have put away 2000 calories on waffles and fruit alone.
We knew we could order some stuff for him out of pocket, but we never needed to. At table service places, you have to pay a tip anyway, so it's no big deal to add an extra side or kids' meal out of pocket, if you want. When finally leaving WDW, we still had 2 QS meal credits and 4 snack credits left, which we just used at the resort QS to take away a big pizza and a bunch of Odwalla drinks for the long car ride home.
Also, we did pack some fruit, bars, etc. that we brought around with us (e.g., grapes in tupperware). These were great for the 19-mo-old when waiting at rope drop in the stroller, or when he started to get cranky at 10:30 am, etc. It doesn't make great financial/practical sense to carry around a bunch of your own food when you have the DxDDP, but young ones are happier eating small meals more frequently, so you might just want to accommodate that for your infant.