Frank,
Welcome aboard! immediate family members (wife & kids) travel on your seniority number at priority S-3's, with 6 higher priority S-2 passes available a year based on your anniversary year. Your parents travel on your seniority number but at a lower priority S-3B's - these are below direct family but above buddy passes. I am not sure where retirees come in at but am pretty sure it is below you and your immediate family. Priority is pretty much - paying passengers, company business (positive space non-revs), S-2's, S-3's, S-3B's, and bringing up the rear buddy passes.
You can non-rev on most of our code shares (Air France) etc and our connection carriers but can not use your S-2's on most if not all of them. Not sure how your dad would non-rev to Bangkok but Frankfurt should be fairly straightfoward. First check the loads on the travel net and then list whovever is going. Double check everyone has all the required documentation - passports etc. Go to the airport and print out seat request cards via the kiosk using your non-rev pass rider cards (blue credit card looking thing). This will allow your family to run the TSA gauntlet and get to the gate. I would always use an S-2 going to Europe. As far as picking flights and determining if you can sit up front - that is part science, part art, and mostly luck. The more you non-rev the better you will get at picking flights. Mid week travel is generally much better. Dress codes for first class are relaxed on mainline - don't know about code fares.
There are also a few gothcha's that you need to be aware of. Certain flights might show a lot of open seats but be limited on non--revs due to a lot of cargo etc. Check the travelnet website (accessed via the DELTANET) for advisories and travel information. I would post any specific questions on the DAL ALPA website under the nonrev travel section. You can get very specific information on destinations and flights etc.
Good Luck - Scoop