Shaffer is a rather common name that is spelled too many ways. This will get you started:
The WWI draft card shows George Leo Shaffer of Allentown, PA was born June 28, 1884. George Leo Schaffer's WWII draft card shows he was born in Leithsville, Northampton County, PA. Leithsville (pronounced Lightsville) is a small town below Hellertown near the Bucks County border. Both records show he was married to Mame.
They appear in the 1930 census with the children you list as living in Allentown and it indicates they were married ca 1905. This time the name is spelled Schaffer. The same is true of the 1920 census except the name is Shaffer.
The 1910 census of Allentown has the Shafer Family (misindexed as Shaper in Ancestry) again.
The 1900 census of Spingfield Twp., Bucks County, PA (next to Leithsville) includes a George L. Shaffer, born June 1884. He was the son of Cornelias, born Sept 1846, and Amanda, born May 1846.
The 1910 census shows Cornelius and Amanda living in Richland Twp., Bucks County. The 1920 census Cornelius and Clementine A. still living inRichland Twp. In the 1930 census they are living in Richlandtown, Bucks County.
The 1880 census shows Conelus Schaffer 32, Amaid 31 and son Orwin 10 living in Springfield Twp. (the enumerator must have been a terrible speller or perhaps just drunk).
The 1870 census shows Cornelius Shafer and his wife Clementine living withElias Shafer 49 and his wife Elizabeth 40 in Bethlehem, Northampton County, PA.
Elias and Elizabeth were living in Upper Saucon Twp., Lehigh County in 1880.
Elias and family were living in Rockland Twp., Bucks County in 1860. In 1850 they were living in Milford Twp., Bucks County.
Some of these records you can look at for free at beta.familysearch.org and Ancestry.com. For those you cannot see for free I suggest checking with your local libraries to see if they have Ancestry or Heritage Quest.
There are a number of sources you can check, but always confirm rather than assume. I suggest getting George's death certificate and obituary. They should confirm who his parents were. You could also get a copy of his marriage record. Most likely he and Mame got their license at the Register of Wills Offices in Lehigh or Northampton, but possibly Bucks County. It will of course have Mame's maiden name and may have data on their parents.
Although you are dealing with a common surname easily spelled several ways you are also dealing with three counties that have very good genealogical sources. They are the Bucks County Historical Society, Lehigh County Historical Society and the Marx Room at the Easton Area Public Library. They have church, cemetery, old newspapers, family history, some court and other records that can be quite helpful.
The Register of Wills offices in the three counties would have estate files, orphans court and guardian records. They would also have births and deaths 1893-1905. For births and deaths after 1906 the PA Dept of Health would have them. Also at the courthouses the Recorder of Deeds has some records that are helpful in genealogical research. But try the other sources first. Also don't get too hung up on exact spellings especially when dealing with a name like Shaffer.