A lot of the basics of bike touring are covered in the "how to" articles on this website, so I suggest starting out by browsing those articles and then asking specific questions here about whatever remains unclear. The route maps for sale on this site have a lot of information about where lodging, water, food are available along each route, and about the challenges of each route and at what time of the year each is feasible.
As far as tipping in American bars and restaurants, my own rules are about as follows:
For full-service restaurants: 15% of the bill for acceptable service, 20% for "very good" service. Opinions vary on whether you should calculate that based on the bill before taxes, or after. I think calculating it before tax is fine.
For establishments with partial service, such as when you order at the counter and they bring you your food, silverware, etc., (but they don't keep coming back and providing more service) I tip maybe 5-10%.
For counter service in a place with a tip jar: leave a few coins behind if you like. If the employees aren't really serving you from behind their counter, tipping them is purely optional. I generally drop 25 cents or 50 cents into the jar when I get a coffee drink and a muffin somewhere like this. I drop a buck or two in the jar if I'm getting a couple of sandwiches and drinks.
In a bar, I am ashamed to admit I have less experience. But I think 10% to the bartender (if there's no table service) seems about right. If a server or the bartender is really waiting on you, then 15-20%. Legal drinking age varies by state, but your 21 or 22-year old son will be good to go in any state. He should be prepared to show his ID (passport, in this case) to verify his age.
Some of the more corporate-type fast food restaurants, such as McDonalds, have neither full service nor a tip jar on the counter. Tipping is not at all expected in these locales, just as I believe is the case is in your neck of the woods.
As for gathering bike touring knowledge, you have plenty of time to learn the basics before your trip, so don't worry. Just keep biking and accumulating knowledge and you will have plenty of time to pull this off well. Make sure to plan some short "practice tours" before the big trip, and field-test your gear and yourselves. That practice, too, will answer a lot of your questions and worries.
When you know the details of your trip such as which direction you are going on which route, you can get some advice here concerning how to get to the start and so forth.
Also, check out www.crazyguyonabike.com
to get an idea what gear people take and what their experiences are like.