Go through some pictures of your Dad. You will want a few pictures of your Dad, from his childhood through now. You want to cover the basics, if possible: birth, marriage; children and his parents and grandparents and family. Using a timeline, place these pictures either in grouped photo frames; a new photo album or scan them and create an online photo album- such as through ancestry.com.
Next, below each picture, say something about that photo, such as names, relation to Dad; year; place and occasion. If you do not know, just say something nice about the picture- what it says to you.
Then, write down a few memories of your Dad. Also, write something you would like to say to your Dad. Place these stories with the pictures on a separate frame; photo album page or scan it and add to the online photo album.
If you know, write down your Dad's lineage. If you do not know your Dad's lineage, you can join ancestry.com for 14 days, for free, which will give you enough time to find a few or more of your Dad's ancestors. Make a name list, with Dad's birth date and place of birth. Above Dad's name, list your Dad's ancestors. Write each of his parent's name's, birth date, place of birth; death date and place of death if they have died. Also list the maiden name of all females. For example: Mary Smith (Maiden: Jones). Below Dad's name, list your Dad's descendants: children; grandchildren and great grandchildren.
Now, you have your Dad's complete legacy organized. What a perfect gift for Dad on Father's day. If you want to go even further, with your Dad's legacy, you can choose to add a gift membership from ancestry.com, so Dad can have fun discovering ancestors and their history that he never knew about. This is a living gift of legacy to your Dad, which will last for all generations to come. Dad will enjoy this gift of legacy, on Father's Day.