@dirtydish been many many years since my sons were home and had to worry about what they did on the net, and the net was a much different place 20 years ago ;)
But pfsense can act as your proxy, you don't need to setup some laptop to do that.
https traffic can be difficult.. There would be a very steep learning curve sadly to say.
If they are using tablets and iphones - you might be better off using the tools meant to monitor those..
https://support.apple.com/en-us/HT201304
I do a bit of this with my grand daughters phone - she can not install any apps without it asking me for permission.. I get a notification - and she texts me ;) Pa can you approve ;) -- she lives in California..
You can also look into monitoring youtube history, etc. Such tools will most likely be easier to get going with and easier to manage and use than say some proxy log that is for sure.