Oh my goodness, your kids are adorable! And the pictures of their packed items is really cute.
Based on what I'm seeing in the photos, here are some thoughts:
- The pillows--I see that they are sitting next to the backpacks but not packed inside. Do the kids carry them separately? Do they get squished into the backpack? Are they like security blankets? That is, do they feel insecure without those exact pillows? Or can they be any kind of soft cuddly pillow? If they can use ANY kind of comfy pillow, there are some travel pillows that pack into smaller pouches. They aren't inflatable or the crescent-shaped travel pillows, but are often made of down and can be squished down. If your kids pack the pillows into their backpack, a packable travel pillow may save some space.
- Those MOBIL people toys in the plastic cases... the toys are relatively sturdy; could you entertain the idea of using a little fabric pouch to store those? Either a zippered organizer pouch, or a stuff sack (both of which TB sells)? The fewer hard boxes they have in their packs, the more packable the backpacks yet.
- Your daughter's packables include two plush toys... do you think she could manage with just one? That will also free up some room.
OK I'm gonna say it again--just adorable!!!! ^_^