Agosos, no worries, I like doing stamps.
Good idea for your son. Computers and game systems are hard to compete with.
The US stamps you have shown look (to me, who doesn't know US stamps too well) like more or less common, non expensive type's of stamps. Just to get that said first. Other than that they can be fun to learn about.
There are two circular cancels or postmarks (CDS)(circular date stamp) on the two airmail stamps on the first page. The first one is nice because it shows the complete date, missing some of the name but hmmm, a puzzle to be solved.
I think the stamps are mostly from the 50's - 70's (not sure). Most stamps around the world were engraved before then and look like they have more detail in them. Newer stamps have more colour or fancy printing processes used to make them. In this era the design of the stamp was the striking thing usually.
First picture, second row, the first three stamps are from the Presidential series (are known as prexies) and are mostly common but fun to collect. They look nice. You can get into the pre-cancels used to put the city and state on the stamp so it didn't have to go through the regular postal sorting processes and saved time. Hundreds and thousands of those.
To learn more than you ever wanted to know, searching on this forum (and on the internet) is a great way to learn a little more or a lot more, depending on one's interests at the time.
There is a lot of history in and on stamps. But you don't have to enjoy history to enjoy stamps. Topics, themes, ideas, inspiring people, stuff related to your other interests (sorry, not many xbox stamps out there yet), art, design, colour, animals, planes, ships, flags, airmails, zeppelins, balloons, umbrellas, definitives as apposed to commemoratives (common small stamps compared to bigger rarer (not as many printed) pictorial stamps).
Usually people like the bigger stamps first as they are very nice to look at. Not just a Queen or King or President to look at. You might feel you are getting a bigger bang for your buck perhaps. When starting out on a stamp journey (I like to think of it this way) it is probably best to do only what you want to do. The way you want to do it. The details will come in time. That's a powerful draw of stamp collecting.
However, to motivate another person to want to do something of their own free will, well, that requires a whole set of skills that not many of us have altogether. There is a very general idea that before age 10 a child listens. After age 10 they do not listen so much, but they watch. I know, scary isn't it? But it's great too. Humans operate this way. Oops, I wondered off into the whys and wherefores again. Sorry.
Doesn't have to be expensive. Can be, but doesn't have to be. I forget how many different stamps there are in the world. Some people start out with just their own country or region as the stamps are more easily attainable. Freebies are good also.

My grandmother saved every envelope that came her way. I got some to start out with. I learned. I made mistakes. I learned some more. I collected everything for years. Stopped. Knew enough to help someone else with stamps. Got myself interested again. Said I'd just collect the personalized stamps like my avatar picture. Learned more. Helped someone else sell their stamps. Learned more. Can't help myself now. All stamps look great to me. It's too late for me, save yourself!



Well, that's one way to go about it. Lots of different ways. Go with your strengths, go with his strengths.
Oh, yes, your question about the stamps stuck down. Well, because they are postally used stamps and no longer have their gum or glue or adhesive on, you can soak them in warm water for about 5-10 minutes (depends on what is sticking them down) and see if that releases the gluing. Won't hurt these stamps. Some olde stamps you have to be careful of. When in water for a bit the stamps become more or less tearable so be gentle taking them out and laying them on paper towel or newspaper to dry. When dry mostly you can press them between books or something flat for a few hours, otherwise some stamps curl.
There is more to this just as there is more to stamp collecting. There is an art to soaking. Many articles have been written. Just be gentle and patient. It helps to rinse stamps out of the first batch of water in another cleaner batch because the first has glue and dirt and what not floating around in it after a time.
See how much you've learned in such a short while? Isn't it great???? Don't you want to learn more?
Again, there should be a prize of some sort when one has reached the end of my post. Hmmm. Maybe I could make a personalized stamp about something. Yes, that's a great idea. Well, I'm off then. Oh, you mean a prize for you? Hmmm. I'll have to puzzle over that one for a bit.