If you choose to repair the damage to your son's car using your insurance, you will need to file a claim and tell your insurer what happened. The claim will impact your rates, but removing your son will not impact your rates as much as leaving him on there — because he has a DUI on his record, that would increase rates in addition to the accident. If you have any questions, don't hesitate to ask.
As long as you can provide proof of a separate address, you should be able to remove your son from your policy completely. Every company is different so you will need to check with your specific company.
Since your son lives in his own home at college, you will not have to add them to your policy if they drive your car less than ten times per year, with most companies. Some insurance companies offer a discount if you add a college student who lives away from home and has limited access to the insured car and seldom drives it. Every company is different so I would check with your company for their specific rules.