Memory Maker's advance price is now $169, so you need to buy at leasst 11 photos to make it more valuable to buy it vs purchasing a few photos at $15 a la carte.
Things that make MM worthwhile
- a big group traveling together
- people interested in stopping at the photopass photographers stationed around the parks to get family/group shots (we stop at least once in each park for the "iconic" photo infront of the castle, Epcot ball, tree of life, etc)
- doing things like Jedi Training, BBB, Enchanted Tales with Belle, I think Pirates League where a photographer will be snapping away the whole time
- doing character meet and greets
- Character meals don't matter, except at CRT, Akershus, etc where a photographer takes your posed shot with character before you are seated (otherwise, you take your own pictures during th meal when the characters actually come around to your table)
- riding rides with photos: Space Mountain, Buzz LIghtyear, Splash Mountain, 7 Dwarfs in MK; Expedition Everest and Dinosaur in AK; Tower of Terror, Rockin Roller Coaster in DHS; Test Track in Epcot
The more of those things that apply to you, the more likely that it will be "worth it" to you. I had about 250 pictures with my big family group in October before adding borders and stickers. After adding maybe 50 of those, I donwloaded around 300 pictures. When it came time to actually scrapbook, of course some shots were simliar (take 4 shots at one spot and choose the best one) but I still used at least 100 in my photo books, so I LOVE MM and consider it worthwhile.
It sounds like a good idea for your trip, but if you're hesitant, you can always just buy individual pictures. I used a lot of my MM shots, but if I had to eliminate it, I could have chosen a dozen or so very best shots to commemorate the trip and been ok.