1: Get tracing paper and a charcoal pencil. Do a rubbing of the wifi plaque, the engrave should come across pretty well.
2: Make a photocopy of the rubbing.
3: Get two pieces of construction paper, white and black. Cut into a large number of 1" Squares. Use that photocopy as a guide to make a sort of jigsaw puzzle of your QR code.
4: Open your laptop in the other room and get Inkscape going. Make a black and a white square. Enlist a second person to yell out the sequence of your puzzle pieces from #3. Copy and paste your squares and snap the corners together to make a grid that matches your QR puzzle.
5: Almost there! Take a photo of your Inkscape screen and text it to your brother. He’s smart, he’ll figure out how to email it back to you, probably within 24 hours too!
6: Download the attached photo from the email and submit it to a QR decoder. There are lots of them, but here’s one: ZXing Decoder Online
7: Copy the SSID and password onto a new piece of paper (you kept the pencil from #1, right?)
8: Start a facetime call with the gkids. Hold your phone up to the SSID and password from step 7, and have them read it aloud to you as you type it into your laptop.
So as an IT guy, here’s the easiest option you can offer. Have a second QR code. This one only shows up as a text image with the SSID information and the sign in password. This may be something that you would want to have on a separate item. However, in doing this you can control who does and does not have password access to your wireless. Additionally, the IT guy in me also needs to make sure this is pointed out. Most dual band wireless networks these days have something considered a guest network. If you have somebody coming over who you do not want to affect your actual network items, put them on the guest network for the love of everything.
Do laptop cameras read QR codes and interpret the wifi: tag to setup a wifi connection? I wouldn’t expect that to be the case. I know Windows requires a separate app from the app store (Wi-Fi QR Code Scanner) to do that. Not sure about Macs.