One low-tech solution would be to create two reports, one on top of the other. The first would have the lowest and highest date values and nothing else. The second would have the data you wanted to report on. I'm pretty sure with List Report there's a way to get just the distinct min and max... maybe not though.
The other alternative is to create a stored process to do this. A stored process is a SAS program with a few tweaks that gets registered in metadata and can be surfaced in many SAS platform applications (including Web Report Studio). You can create stored processes in Enterprise Guide, SAS interactive windowing environment (where you'd write and submit SAS code), or I suppose any text editor in the sense that SAS code is fundamentally just text. EG is probably the easiest way to develop a stored process because you get all the point-and-click tasks, plus there's a Wizard that handles the necessary "tweaks" to get from SAS program to stored process. Using Macro variables in the stored process code, it'd be easy to create a title with the Min and Max date values. That is, if you're comfortable writing SAS code. 🙂
Others may have some better ideas... but I can't think of a way to separately capture min and max in a "title" aside from what I described above.
Richard