I don't advise booking a package. Prices go down very frequently at the onsite hotels. If you just book your room from loews, you can adjust your prices as they change without any penalty.
I've yet to see anyone getting a better deal with a package.
That sounds a good rate, wouldn't want to stay that long though as my DD doesn't really like US/IOA, though I am hopping that as she will be older next year she will like it more.