My DD (8) loves meeting any and every character, and autographs are mandatory for her. Luckily, I also love the characters and photo ops. We haven't yet sought them out, but we usually stop if we see someone. DD enjoyed it more on our 2nd trip than the first, and I was much more willing to give up "touring" time the 2nd time around.
If this is your first trip, you'll have to feel out the kids to see if they are interested. You of course have a say in how much time you're willing to spend collecting the autographs and meeting the characters. But with 3 character meals, you'll definitely have enough for a nice collection.
On our last trip, DD was so funny, kept telling me, "oooh, that character is really rare!" *(Kenai from Brother Bear, for example) As if she has a clue who is rare or not.

I had such a blast watching her excitement getting these "rare" characters' autographs!!!!
Oh, yeah, and for our last trip, she had her own draw-string backpack for her autograph book, pens, hand sanitizer, etc. She felt SO responsible having to keep track of her own stuff. And less for me to carry!