If you don't know how to tie a patka, you may also need some help tying a proper jura. Here is a delightful - dare I say adorable - video of exactly how to do that.
I have two suggestions for mata ji:
1. Don't pull the upper ponytail too tight or your hapless son will develop a receding hairline.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/sikh-youth/17633-how-to-tie-a-patka.html
2. This can be a very special time for the two of you. First, because he is actually holding still, it's a great time to find out what's on his mind. And second, because you are engaging in an activity that is specifically Sikh, it's a great time for Sikh education. Be creative! We used to sometimes naam-jap together using different melodies.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=17633
Chardi kala!