I love Memory Maker! It's not a replacement for my own camera, but I adore ride photos and have a collection of every year with nighttime castle pictures (and I can never get those right with my own camera). At character greets (not meals, but meet and greet lines) I sometimes use my camera for video and rely on the Photopass for still pictures (but you have to watch the few groups in front of you to judge is the photographer will just take the posed picture at the end or if he/she will take candids along the way). You also get the magic shots along the way.
If all you want it for is character meals, then I wouldn't recommend it. But if you want lots of photos for the whole week, I'd recommend it. Your kids are old enough to be on plenty of rides with photos, so you'll get your money's worth on that. Even the 3-year-old can get ride photos on Mine Train (if you have Magic Bands). And one year at
Disneyland I found a not-busy photographer who took us on a mini-photo shoot around part of Fantasyland. She posed us all over the place and I got great family photos (perfect for the Christmas card that year). A different year a photographer saw my son and I in Frontierland and took a bunch of great pictures of us by the river. Some of my favorite pics of us together!
Another thing to remember is that you'll get the photos from Enchanted Tales with Belle if you have Memory Maker. I find it really tough to get a good photo in there (the lighting is really weird and kind of blue-ish) so I'm always glad I get their photos, especially if one of my kids is chosen as the Beast.