There certainly are lots of caves and castles around to visit, but I agree that it's not always easy to find useful information online; it's generally better to get personal recommendations

Just this week I purchased the book The Surprising Wines of Switzerland, and it contains quite a lot of helpful information that might be of assistance to you as well. I picked it up at Payot; I think Orell Fuessli is the equivalent in Zurich, if you're interested in getting your hands on a copy.

My personal recommendations for Vaud are:

There is a Vine and Wine museum in Aigle that you might find worth a visit, given the nature of your trip. I'd also recommend taking a walk through the Lavaux vineyards; this is the bit that was recently designated a UNSESCO World Heritage Site. The scenery alone makes it worth the walk, and as an added bonus, you should be able to squeeze in a few visits to caves as well. (My favourite Swiss wines are the ones from Epesses.) I wrote a bit about this hike on this thread. If you can squeeze it in, a boat ride on Lake Geneva is definitely worth doing.

Regarding castles, the Château de Chillon is a must-see. Even though the site is crawling with tourists, it is with good reason: this is probably the finest and best-preserved castle in Switzerland.

I haven't read this myself, but there is also a food and wine section at myswitzerland.com that might be of interest to you.

I hope you enjoy your trip.

HeatherM