We only used Arabic, which I don't speak *at all*!
I wouldn't buy it for the kids unless I were either pretty serious about learning the language myself from scratch (and I wasn't about the Arabic) or I already spoke it. Since you already speak it, I think you could support your DS in using it. I just couldn't do that for my DS with Arabic.
It is something you need to do regularly. Once a week probably wouldn't cut it. Every day for 5 minutes a day would be better than half an hour once a week (or even half an hour twice a week.)
If you're still on, you might check this out:
https://www.homeschoolbuyersco-op.org/index.php?option=com_hsbc_epp_order&Itemid=1091It was recommended to me over RS for kids by several people I trust, and it's deeply discounted. It expires NOW though. I think you have a day!