After countless trips into the parks over the past 16 years...I can't remember ever having a problem keeping our kids from getting bored in line. All of my children have been going since they were less than a year old (with exception of my oldest who was 4 years old her first time to DL...). But even when they were babies and toddlers, I don't remember any issues (and believe me...I get annoyed pretty fast with kid-whining, so I would remember if it had been an issue because I would have resorted to not going until they were older if it had been a problem).
We never eat snacks in line, mainly because my kids have their hands on the railings througout the queue, and there is NO way I'm letting them touch anything that's going to go into their mouths after that until they've washed their hands, lol.
We DO, however, put a lot of effort into avoiding hunger-induced-grouchiness while in the parks. We make time mid-morning to stop, sit down, and have everyone eat healthy snacks we've packed in (sunflower seeds, yogurt raisins, raw apples, yogurt cups, carrot sticks, bananas, etc.). We do this again between lunch and dinner (basically, we just finish up any snacks leftover from the mid-morning break).
My kids spend a lot of time just looking around and observing while in line. We do what we can to avoid extra long lines (I would have never waited longer than say, 20 minutes, in ANY line with a toddler, for instance...), and that helps.
This question has rolled around the boards before...and I think I probably mentioned on one of those threads that if my kids complained about being "bored" at Disneyland, I'd leave, lol. And they know that about me, so even if they *have* been bored in line, they've known well enough to keep it to themselves.
My children are older, though. I know it's an entirely different ballgame when they are toddlers and preschoolers. Good luck, I hope their surroundings hold lots of interest for them in line, and that you all have a really great time!
