Oooh! I just saw this post! I've had a similar issue and never thought of posting on here!!
We head out to church on Sundays just as he should be going down for a nap. The little booger doesn't sleep in the car on the way there and he simply won't sleep on my shoulder, so he's basically up from 7ish AM to noon w/o a nap. Considering how spirited/touchy he is, he does
extremely well!! I think it's because there's enough going on around him so that, even though he's exhausted, he',s kept 'entertained' by the other busy bees (the kids in the cry room). We don't even need to be in the cry room since he's so quiet but we go there just in case.
When he was smaller he would sleep in his infant seat - those things are SO wonderful! I wish they had toddler seats that were as easily transferable. Someday.
Shimmer, it's definitely okay to let her sleep on your shoulder once a week. It won't throw things off.