I would think plugging the web site would be beneficial in the letter?? I'm about to work on a batch of letters today that plugs the web site and I also will include my business card. We'll see how it goes!
There's a company out there where you can fill out a template and they will convert your handwriting into a text for typing up letters. I think they charge $10 for their basic conversion (which should be all you'll need). You can then use mail merge to automatically insert their name. You can also print the address directly to the envelope. This will make you 10X more efficient.