I think I have a chance of convincing him for a few reasons:
1. I'm about to go off to college, which will leave him having to maintain our computers.
2. My moms desktop has 256mb of (old, non DDR) RAM, and her laptop has 128... both need replacing.
3. My mom is a doctor, so a lot of her friends have macs.
So it shouldn't be hard to convince my mom that she would like to have a mac, and if its easy to set up and maintain, and compatible with the software she needs (mostly just email, browsing, and a VPN client she has no idea how to use) then my dad won't have much excuse left. I think a Macbook (keeping in mind this will be 6+ months away probably) with a monitor for use at home would suit her needs quite well.
But now I'm getting off topic... Off work in 10 minutes, go home, get the Fed Ex paper (the delivery failed this morning because my sister was sleeping), and go pick up my MBP