I need to share my desktop remotely with my son

You could also consider Apple Screen Sharing (which uses a variant of VNC protocol), but off-Network would likely require you to do Router port-forwarding of TCP port 5900 from your Router to go directly to the Sharing Mac. Using a manual IP address for that computer would be more stable in the long run.

If the above is all "word-salad" to you, it may be more than you want to wrestle with.

I would use TeamViewer.

If you goal is only to share a document, you have a number of "free" choices to do so:

1. Email - Just add the document as an attachment to an email message.
2. iCloud - How to Share Files Stored in Your iCloud Drive - MacRumors
3. Dropbox

No problem, I did understand that you were looking to use remote desktop sharing. I just thought I'd provide you with an alternative.

Until BobTheFisherman replies to your question, I believe the answer is "yes."

https://www.teamviewer.com/en-us/download/mac-os/

Yes and he can to do the typing if you allow him to.

You are welcome.