Take a close look at Irfanview, it is freeware and has batch resize.
This program makes it possible to load all original images and store a altered version in another directory/folder/map, so it shouldn't be too much trouble creating your thumbnails. Only point is there is no jpeg compression preview, you have to learn by trial and error what is acceptable. For thumbnails I often use something between 40 upto 25 compression, depending on the picture itself (smooth backgrounds are more prone to show jpeg artifacts than lively scenes).
Irfanview can also create a webalbum, really basic style, but it can be usefull as a start html to edit on.
If you get stuck with Irfanview or any other programme, lower in Steves Forum list is a software section.