The pre-opening line isn’t really a “line” until it starts moving. It’s people hunkered down on distanced markers, possibly for hours. While a while group pulling their masks off entirely and laying down a feast is probably an issue, discreetly eating a snack or sipping some coffee, with masks on in between, is unlikely to be an issue.
When we were waiting at the gates for Touch of Disney, I had a Starbucks and was unhooking my mask occasionally to drink it. My daughter had a packet of trail mix. A few people around us were also finishing up drinks and snacks. Since we were stationary + distanced, that was within the rules. However, once we started moving, everyone’s food went away, drinks were finished and put in the trash, etc.
I’m not sure about passing out food and eating it immediately - could attract a CM to shut down eating, especially if they’re being very attentive to the rules on opening day, which I suspect they will be.