Forgot to tell you!
Try substituting the hotdog and/or packaged noodles ( I assume you are meaning like Ichiban type??) for something else. You wouldn't believe the fat and sodium in there. I don't like hotdogs (all that pigsnout, LOL) but I admit, the noodles are good. But they're so bad for you.
I find what helps me is to actually have something ready before hand (cut up the veggies , have a healthy - ish dip to make it taste better etc) because I like to take what's fast/easy.
I have a one year old now so I have an excuse, right?
And variety. I was so sick for a while I almost ate nothing but wholewheat pasta and sauce, applesauce, pretzels...and crackers I think? Oh man. It was miserable.
And try opting for less canned stuff (also often has lots of fat and sodium).
Try healthier fats like peanut butter, olive oil, avocado if you like them, even some saturated types like cheese and butter etc would be okay in moderation, just become a label reading freak and avoid anything that says hydrogenated oils (bad bad BAD stuff, that). If you already don't put weight on easily, you don't want to go nuts with no fat (makes you sad to hear that, doesn't it??
Even if fat isn't the cause of the runs, it's not a bad thing to miss out on that trans fat (hydrogenated oils).
Really, your diet doesn't sound that bad (except those noodles and dogs), from what I read. Just be really aware of everything you eat for a while. THis is a pain but really helped me - I wrote down everything (and I mean everything) I ate and drank for a month, and really noticed patterns in what was causing me pain and misery. Might help! And you could bring it with you to the doctor...espec if you notice a trend, and the diarrhea tends to happen after eating (does it? or is it more random?)
There are lots of healthy recipes you could encourage your family to try. Personally I don't like to eat healthy if it's not at least okay tasting. Luckily it's better than it used to be, more and more good tasting healthy stuff out there.
Water is good, btw! And low fat milk (Yes, some will argue that....)
I just realised...I really sound like a mom, huh???? LOL! Hope I didn't "nag" too much!