Virginia, This is a problem that any one just starting faces. You feel that you must keep some families apart from others. Let me asure you that this is not needed with todays genealogy programs. The programs can handle in one project thousands of persons without any problem. Early programs were limited in the number that they could record because of the computer memory or disk size.
Now if you were doing research for some friend you may want to put them into a new project so that you may delete the project later.
Also another hang up that starting users have is the numbering system. Forget about numbering and let the program number the person. These numbers are only for the program to keep track of people and an aid in finding them later.