Hi, Carla,
I think it depends on how the document must be delivered. If it's a
presentation, use PowerPoint as the default. If it's for storage /
archiving or e-mailing, Word might be the best bet. If most of the data is
spreadsheet data, then Excel might be the best basis for the document.
Now, if you are only storing it, you may want to use a compression program
such as WinZip to "clip" all the files together in one single zip file,
instead of actually combining the content.
Without seeing your files or knowing what it's for, my bet is Word would be
the easiest way to combine content. Fortunately, all three of the
applications do a good job of understanding each others' formatting, so you
shouldn't have to do too much to get it all in one.