The 1st Whitman editions

In the late 1940's, the copyright on the first three Bobbsey Twins titles was not renewed, leading to several companies offering reprints of these 3 titles.  They were all of lesser quality than Grosset & Dunlaps, but Whitman knew how to sell books with new artwork.  Unlike the other two publishers (Goldsmith and Sallfield), Whitman issued individual artwork to each book, and updated that artwork twice, after these initial volumes were released. 

These first 3 were released in dust jackets with interior artwork by Janet Laura Scott. 
It appears the cover artwork is also by her, although the artwork is not signed.