- Chromecast 2 or Chromecast Ultra's make great gifts.
- Kindle Fire's can be bought in bulk, engraved, and pre-loaded with content. So if you're doing this for a business conference you could for instance pre-load the conference app or some business PDFs on them as well as customize them. Amazon offers bulk purchasing through their business relations team.
- I would go with a portable charger for around $30 USD, which is good for nearly 4 full phone charges. If you want to go above and beyond, then I would also include the Anker PowerLine+ Lightning or Micro USB cable for $10-15 USD. I specifically recommend the PowerLine+ because it's a nice sturdy cable that's also braided.
It takes a while to get used to but is a great way to learn Linux. Originally designed for school childeren but great fun for grownups too. If you want to learn a little bit more about computing, get yourself a Pi 3 and get started! recommended!
It's a mammoth packed in ant body, one can do much more but to start with it is bit hard.