I agree that a handheld digital recorder will get a lot of use, not only at the Song School but in many situations. The Zoom H2 is about $180 and Tascam DR 5 is about $100. Both record on SD cards so it is easy to transfer files to a computer and of course you can always listen (I use ear buds) to the recordings directly on the recorder. Depending on your access to batteries (I have gone to The Swannanoa Gathering for the past six summers and was able to use rechargable batteries and recharge them in the dorm at night) you can record (with instructor's permission) parts or all of sessions as well as songwriting ideas, etc. Most phones have recorder apps which are fine for short ideas and recordings but a separate recorder will usually provide a better sound, be easier to transfer files, and not drain the phone battery.
I find a gig bag (rather than a case) easier to carry my guitar from session to session.
Another idea is a Cooperstand guitar stand
https://www.cooperstand.com/products/ecco-g I really like them because besides holding the guitar, they fold up nice and small and will fit in most cases under the headstock and in gig bags in the pocket on the front.
How great for your niece to have this experience at such a young age.
Listening to:
Janis Ian