I had the same problem trying to find where my grandmother is buried. If you have an Ancestry.com subscription you can do what I did - look up an obit. The Washington Post and the Washington Star (now defunct) obits are pretty good. If you do not have a subscription please send me particulars on the McCallums you are searching like full names, dates even if very approximate, any other information that might be in the obit like who might be referenced in the obit (their children and childrens' married names, etc).
I am really persistent and have had remarkable success and I would be happy to look for you.