Most everything at DL is kid friendly, including Blue Bayou. Most kids like the atmosphere with the fireflies, the boats going by, etc. My son seemed to like Blue Bayou fine when we went with another family when he around 7. However, I took him back when he was around 10 and he didn't like it. I think the problem was, the kids menu indicated ages up through around 9, and he felt he no longer made the cut. But the costs and the selections of the adult menu were not appropriate for him at that age. We ordered off the kids menu, but I think he felt uncomfortable with that. Now he's 14, has an adult appetite, more adult tastes, and loves for me to spend money on him, so he likes BB better again.
It's now been 4 years since we've ordered off the kids menu, so I don't really remember what it offered. I think it's pretty standard -- chicken strips, pasta dish, ... I believe the menu is posted outside, so you can always make a reservation and cancel if it doesn't look like it will suit your family.
I believe you can make PS 6 weeks in advance for Blue Bayou.
Lunch is a great option. It's a little cheaper, although it may not affect the kids menu prices.