I would like to allow my living children to see my genealogy chart. Can we merge information, or can

Only the person who created the entry can see living individuals. Your children can see everyone in your chart who is deceased.

So your son would create an entry for himself even though you have one for him also. He would also create an entry for you as his mother and one for his father if he is still living. Assuming his grandparents are deceased, he can add them by ID number and you and he will be attached to and seeing the same deceased individuals.