For the kids at the restaurant while you're waiting for your food: DIY busy wallet! pick up a cheap wallet. fill it with pictures, scrap scrapbook papers, stickers, a pen, etc. ***CJ loves taking apart our wallets.
Laminate a set of flash cards, put a binder ring around them, and toss them in your purse with a dry erase marker to entertain little ones. I don't know about the dry erase part but LOVE the binder ring!
spray paint measuring tape and keep track of kids heights at different ages. Takes up no space and can move with you. I would paint the back side to mark so you can still see their height without having to remeasure your measuring tape.
FREE Back to School Chalkboard Printables from kindergarten all the way up to senior year! Take photographs on first day of school every year for your kids scrapbook. Photo props for children and teens