Thanks for the suggestions. I love Singapore workbooks they are really well done. I use them mostly as a reference just to know in which order they introduce things. Dh and I are both into math and we sometimes get into interesting problems and forget that DS better learn the basics first. Lately DS has been doing exercises from the workbooks because that's what his heart desires right now. May be I should leave only the challenge workbook (I have only one) lying around.
We do beestar GT together. It's a nice way to come across different problems and concepts. Time to sign him up for the next session if he still wants to do it.
I checked Alex long time ago and at that time it was too early, but it would be probably a good fit now.
