"Even now that they're ten and almost twelve"? I think my brother and I played with Legos until I stopped having time for them due to schoolwork, which was probably around when I was 15 or so. And it was as much a case of not having time, as it was no longer being interested.

Another entertaining thing about Legos was that, when I was talking to the graduate admissions office in MIT's mechanical engineering department, one of the people there made an offhand comment about "and please don't go on in your application essay about how you want to be an engineer because of playing with Legos as a kid; we get so many of those essays."