I suggest you animate on a higher frame rate 15fps is what most people use but you can get away with 12.

YOUTUBE TWITTER

Time to get some new software.

QuickTime 7
Its the old version of QuickTime which actually does stuff, unlike the new QuickTime. For the feature you will need, I believe you will want the pro version, after downloading QuickTime just look on google for a registration number and out that in QuickTime in settings. Or you can buy it from (I believe) the Mac app store or apple.com
To make the animation (excerpt from the user manual):
Put all the graphic files you want to include in a folder.
Name each file with the same name followed by an increasing number; for example, “picture1,”“picture2.”
Most digital cameras number files automatically. The numbers must be increasing but don’t have to be precisely sequential (for example, you could name the files “picture1,” “picture5,”“picture10,” and so on).
In QuickTime Player, choose File > Open Image Sequence, and then select the first file.
Choose a frame rate (the number of frames displayed per second) from the Frame Rate pop-up menu.
From there, export it and add music or whatever in iMovie or some other free editor. In QuickTime 7 you can also do basic editing, so see what you can do with that. I've found a few open source/free animation programs for Mac but most of them are outdated and discontinued or don't export at the resolutions I like.
BTW, I edit on my Mac in FCP but I wouldn't get that if you're just doing Brickfilms. I use QuickTime like this when I want to do quick previews of my shoots.
If you have any more questions, ask away, I'm all Mac and have lots of experience brickfilming with them, so I can probably answer most questions.