try to open them with iMovie. If you where able to import them, click share, export with quicktime, click movie to quicktime movie, choose ether broadband low, or broadband mid, they will both give you pretty small file sizes.
If you want more options, click on options. under settings you can drag n' drop the slider towards low or high, and you can adjust the frame rate. under size you can adjust the video size. I would reccomend using H.264 as the video codec (under adjustments)