I sprung for the ranger vest and the passport book. We (50yo mum with 11yo boy) actually fought over who gets to put the stamp in the book! This summer we took a long trip-visiting 12 NP, NM, NL- and we became a bit fatigued towards the end. Until we hit Badlands NP where the park offered multiple patches, which required extra work, in addition to the badge workbook. Finding a fossil in situ was amazing to see in real life (for both of us!) and earned him a patch (the fossil was left for others to discover too). Then some late night astronomy earned him the second patch.
For the several parks that gave patches, they are residing in the big pocket on the ranger vest and the badges adorn the front and back of the thing. I let him put the completed junior ranger books in a binder which he loves to revisit. We came to love the ranger-led hikes, presentations and activities--especially a guitar wielding ranger who led a " Bear Aware!" sing-a-long in Yellowstone-Canyon.
Our road trip cooler is loaded with stickers from places we visit..a lot are freebies. Happy trails!