Sensors are gonna be a bit all over the place unfortunately and with at least 3 I'm keen to explore other possibilities.
Not sure how big the pages are but to give a rough idea this page is ~32k. Mine wouldn't be quite as text heavy but ideally I'd create them ahead of time and store them rather than have them created programmatically.
It looks like the ethernet shield will function as a webserver although I'm assuming that it doesn't have any more storage than the 'duino.