Not sure how you can have a Mac and not have iMovie, as it was included with the Mac (of course you haven't said anything about model, year etc so it's hard to know what version you might have). iDVD is not included on newer Macs, but iMovie, Garageband and iPhoto are.
It is indeed easy to make a DVD that loops automatically in iDVD, but since you don't have it and can't obtain it anymore that's a moot point. As you've already got a solution I'd say just stick with that.