We didn't use a lanyard and it wasn't a big deal. There weren't that many places we needed to pull our passes or tickets out of our pocket. However, we travel with one backpack for our family too, so I could tuck them away easily during some rides. If I were going without kids and thus without a backpack, then I would have wanted a lanyard.
We were just there - leaving RPR yesterday, actually. Unfortunately, we weren't able to watch the Grinchmas show since the line was way too long. We spent several days at US/IOA but this past Saturday was the only day of our trip that had Grinchmas. We tried twice but there was no way our kids could have handled waiting an hour an line. The park was only moderately busy - I'd give it a 5 out of 10. Other shows weren't close to full. So - plan accordingly if you really want to see it. We tried the 11:45 and 12:45 shows - I'm not sure if you'll have better luck with a later show. The 12:45 was worse than the 11:45 as far as the wait.
The dining plan is one snack, two drinks, and one entree. I think it used to be two snacks - as I can remember doing a plan with two snacks a while ago. The dining plan doesn't always make sense - it depends on how you eat. We do it when we plan for Butterbeer and Three Broomsticks as just the chicken and ribs or the rib platter and one butter beer puts us ahead, making the two drinks absolutely free. You can also share meals - we get two adult meal plans and then share our drinks, butterbeers and entrees.
We sometimes take the boat and sometimes walk. Since we were going stroller-free for the first time, we mainly stuck to the boat. However, the few times we did walk, we easily beat the boat - once by a full 10 minutes.
Also, don't forget to take advantage of the early hour. It was IOA the entire week I was there but I didn't see a single sign for it until I was in the parks walking in IOA! It's quite possible I just kept missing it but it wasn't marked well since we had several days and I didn't see it anywhere else initially. At the end of our trip, I discovered a small piece of paper in our info pack that said it was IOA.