My son just signed up for a FS account. How does he get to see all the FH my wife and I have entered?
Only the user who created a profile for a living person can see the profile due to privacy concerns. Due to this, your son needs to create profiles in Family Tree for you and your wife and connect to you two are your son. Then he needs to do the same for any living grandparents and connect his copy of you as a son to your parents and his copy of your wife as a daughter to her parents. Any living grandparent profiles need to be connected to their parents. Then he should be connected to the general tree of all deceased individuals in Family Tree and everything you and your wife have entered on your deceased relatives.
Profiles for living people are private to the account that entered them, so he'll need to create profiles for you and your wife and any other living people between him and his deceased relatives, but once he gets to those deceased relatives, he can connect to the same profiles as the ones that are connected to you. You can make that part easier for him by giving him the profile IDs (the hyphenated seven-character strings found after the names in most places in the Tree).
In my (strongly held) opinion, profiles for living people should be bare-boned placeholders or connectors. Your son doesn't need to spend any time and energy on the profiles he creates for you and your wife. Heck, it's perfectly fine if he enters "Mom" and "Dad" as the names, and in fact, I encourage such an approach: the best way to protect private data online is to not put it online in the first place.
Thank you for those responses!