Just some additional info...
Only one person has the capability to download photos with a Memory Maker purchase. Everyone else will be able to see the photos in his or her Photopass section of MDE, but they will have the watermark.
We only had a family group, but my DD did a lot of touring (and character visiting!) on her own. I was the MM "owner", so when I saw a photo that I knew she'd want to post on Facebook or
Instagram, I'd download it on my phone and text it to her.
When you get home, you could share your sign-in information with the other family, or if you are not comfortable with that, you can download all the photos and add them to an online photo sharing site or upload them to a thumb drive or CD to share with the other family. You could have an "editing party" to add borders and other enhancements, if you'd like!
Hope that makes sense!