To answer the original question...i think the movies can survive with out the original kids...it isn't like Harry Potter, where you couldn't have a movie without HIM.
However, i think they hurt the chances with a couple of things:
1) Release date: i don't think it was so much being close to Harry Potter (at least 3 weeks after), as much as it was the WEEK BEFORE Tron. It reminded me of Star Trek Nemesis coming out right before Lord of the Rings. If i have alimited movie budget, then i am going to prioritize. That year, it was NOT Trek. This year, i think for many, they were saving up for Tron, especially if they were going to do 3-D.
2) Making in 3-D -- Again, Tron, which would be one of the must-see in 3-D mvoies, was just the next week. So it would have been too muchfor people. And withit beingin 3-D, peple might not automatically think it's available in 2-D (i know that sounds dumb...but with all the ads emphasizing 3-D, one might forget)
3) Not marketing to Christians. Liam Neeson's opinion didn't bother me, as Christians have tried to interpret The Matrix (and i think successfully) as a Christian allegory, though clearly not created that way. And the movie, like the 1st one, has mainstream appeal. But not getting the Christian Community excited about this movie really killed the buzz (which helped raise the excitement of Narnia)
i hope we'll see more, but with some better marketing