Linking separate gallery page to each post

I’m trying to work out how to insert a gallery into a post, but for the gallery to show in a separate page similar to the attachment/image page.

So for instance: editing image.php so that it shows ALL thumbnails associated with that post (making the linked attachment the same size as all other thumbnails, essentially creating a separate gallery page), and works with lightbox; or paginating a post so that the gallery is split from the text in a second linked page.

Any thoughts on the best way to do this?

It’s for an events site, so for each event I’d like a description and a gallery. I thought of making each event a category and creating two posts in each category (‘description’ and ‘gallery’) but that would be too messy. It’s for a client, so it needs to be really, really easy…

Any ideas much appreciated!