I had a bunch of photos I wanted digital copies of. I used my ScanSnap S1500 set on high quality photo and got decent results. Printed one of the copies on a photo printer and could barely tell the difference between it and the original.
A flatbed scanner or a camera on tripod will be tedious and time consuming. Make sure you’re up to the time commitment before starting.
Tell your dad that mailing the photos to a scanning service that will allow you to have multiple digital copies is safer than keeping them in the house. I’m thinking about the recent tragedy in Paradise CA. I’m sure a lot of people lost a bunch of photos. An off-site digital copy goes a long way in helping to heal from the other losses.