That's perfectly ok and the way to go. When I publish an addon I use to put it inside a ZIP archive, together with a README file, including information about the source I've downloaded the model from, and about its author. But you may use other approach, if you please.
Giving credit where credit's due is not strictly a mandatory requirement, but it's rather a question of courtesy and respect towards the real author and appraisal for her hard work.
And failing to comply with this rule of etiquette, should the transgression be finally discovered, has somehow unpleasant consequences.
Of course, this relative laxity only applies to works in the public domain. If we were talking of items by someone holding its intellectual property, or copyrighted, things are far more serious.