Photo dilemma

I have a travel accommodation website that has page one SERPs for most of my keywords. WE are doing a redesign that changes .asp to .php

I will do 301 redirects, but my web guy wants to change my current design with a main photo thumbnail page for each area and then an individual page for each photo linked from the thumbnail page. There is content on each page and links pointing back to the main page for that area.

He wants to keep the thumbnail pages and replace the other pages with a lightbox javascript viewer of the photos. Overall site is 80 or90 pages, the photo pages being replaced are maybe half of these.

This seems like a dangerous move to me. Correct?

I assume google is too clever for me to simply put the indiviadual photo pages in with links in place, but use the lightbox for the majority of visitors? Or not?

Thank you for your valuable opinions!