We used some of the
Carson Dellosa "word problems" workbooks for enrichment when DD was 3-5 yo. The Frank Schaffer and Spectrum imprints also have some pretty good titles in this genre.
Another resource for you might be
Singapore Math's "Challenging Word Problems" series, though some of the methodology may depend (a bit) on the particular sequence of skills in their primary math sequence. On the other hand, if you plan to supplement at home, you can't do a lot better than Singapore for most younger GT kiddos.
My DD
ate that stuff up. She used to beg me for more problems out of those supplemental Singapore books.
