Do everything you can to limit what you spend. If you can minimize expenses - including discretionary spending like bars and restaurants - you'll be amazed at how fast the cash piles up. Yes, this requires sacrifice and discipline. And that's just crazy!
Couldn't agree more with Mags - your Dad is supposed to worry about you; it's his purpose in life. Even my parents are worried about me and I've been around the block several times. I would think that after a few weeks on the trail (and some calls/emails/postcards), your confidence will rub off on them and they'll be very proud.