You can explore all of it I think, haven't played it in a while. There are also tours of specific areas as well, like the Pyramids.
FYI if you don't want your son to play the base game due to violence, you can buy the discovery tour versions of Egpyt, Greece, Vikings separately as stnadalone, which only contain the tours and not the stabbing and killing gameplay.
https://www.ubisoft.com/en-us/game/assassins-creed/discovery...
https://assassinscreed.fandom.com/wiki/Discovery_Tour:_Ancie...
You can explore all of it I think, haven't played it in a while. There are also tours of specific areas as well, like the Pyramids.
FYI if you don't want your son to play the base game due to violence, you can buy the discovery tour versions of Egpyt, Greece, Vikings separately as stnadalone, which only contain the tours and not the stabbing and killing gameplay.