It looks like it will be easiest to use a series of images. You could put them all in a single HTML document with heading tags between images, then instruct calibre to page-break on these tags. (If you don't want a header on each page then you could page-break on the image tags instead.)
There is also a tool called
img2epub (
http://code.google.com/p/img2epub/) which is designed specifically to make an ePub from images.
I don't how well a series of images work with most eReaders but my PRS-300 is slow when rendering a full page image. An alternative would be to use some music notation software on your iPad, (but wouldn't help with the Kindle.)