The DUI is a gross misdemeanor and the Attempt to Elude is a felony, so they are subject to different sentencing standards.
With the DUI, there is a maximum of 364 days in jail and a $5000 fine. There are mandatory minimums which apply based on a person's history of DUIs and breath test result (or refusal to take the test). The previous poster gave you the appropriate link to the sentencing grid for the DUI.
The elude, however, is subject to different sentencing guidelines based on your son's criminal history. Here is the link to the scoring sheet that is used to determine a person's sentencing range for Attempt to Elude.
As you can see, your son's sentencing range would depend on the number and type of prior felony convictions and DUI convictions, as well as current DUI charge and the fact that he was on community custody. Based on what you stated, it sounds like he could have anywhere from 5 to 9+ points.
If he is convicted of these new charges, he is looking at a significant amount of time in jail. He should be speaking with a lawyer as soon as possible.
You can find a Court — DUI Sentencing Grid (under RCW 46.61.5055 as amended through January 1, 2011) at (http://www.courts.wa.gov/newsinfo/content/duigrid/DUIGrid.pdf), you would need to plug in the specifics of your son's cases to come up with a possible sentence.
The range of time that your son is looking at on the DUI and the Felony Eluding both depend on his prior criminal history. The DUI range will also depend on what his breath/blood level was or if he refused to submit to a test of his breath/blood. He should consult an attorney who is familiar with the court he is charged in who can look closely at the charges and his prior record to fully answer this question.