There was a program called WINJPEG (shareware) where you could batch reduce. Set the size you wanted the photos and walk away. MAINTAIN Aspect RATIOS!! for sharper output images.

I would make a blank square. where the photos could fit, landscape or portrait. Paste all into blank square , then batch resize.

Watch for compression change. some will compress original too much and you have a lot of 'jaggies' or unusable image. (Keep at 100% for your existing quality)

I had to place over 3000 images of albums in The Complete Motown www.kegtapper.net/TCMC and it was a learning experience. Though I only had to work with smaller sized images.