Might wanna just skip to grade 3. There would probably be plenty in there to interest your kid, even if some of the problems were too hard. OTOH I am sure the grade 2 would have much of interest in it too.
Last year my son really enjoyed some of the reading comp. worksheets too. They sparked an interest in multiple areas of science. I'd check 'em out.
There is also a separate, physically smaller and cheaper line of workbooks by the same publishers, called FlashKids something or other. The problem solving ones are pretty great IMO. I think they're about $4 US on Amazon, and well worth it. (Some of them are drill drill drill, like the multiplication ones, and should be avoided for a gifted kid.)
ETA: Here's one of the "Flash Skills" mini-workbooks I mentioned:
http://www.amazon.com/Problem-Solving-Grade-Flash-Skills/dp/1411434692/ref=cm_aya_orig_subj (this is a good one)
