I have a 12 year old and a 2 year old.
I think a little bit of boredom is unavoidable. He'll have to accept a little bit but I think it's easier if you acknowledge it.
A musical instrument.
Listening to music (and learning the words).
Writing to a pen pal.
Building a cook fire for lunch.
A dart board (soft type if 2 year old will be near it!)
Backyard chickens are fun too, even for a 12-year old. And especially for a 2-year old.
Planning an outing. (Give maps, brochures, toll-free numbers, budget.)
Hand-crank ice cream.
My cousin liked rug-hooking when he was that age!
Tonka trucks and a big pile of sand. Yes, even for a 12-year old. He will feel responsible for showing 2-year old 'the ropes' ie how everything works.
Designing an irrigation system for your garden.
Entemology (so he can tell you what bugs are in your garden).
Get a good reference book for this, that's geographically suitable for your location.
Soil test kit and have him do the soil testing.
A cider press and some apples so he can make cider for you.
(Boil it and cool off before giving to the 2 year old.)
A pair of binoculars (2 year old gets plastic ones!) and a birding guide and checklist.
A mail-order pack of inexpensive world stamps and a world map.
(2 year old also likes stamps)
A tent and camping equipment, the kids can practice camping skills in the yard. Even setting up the tent and digging the trench is a challenging exercise for a 12 year old (but a good skill to acquire in life).
Software such as Rosetta Stone for learning a new language. You can get Rosetta Stone relatively inexpensively (it's a wonderful program for learning language) from www.sonlight.com
Anything that relates to his particular passion in life. Here we have a KNex roller coaster set (2 year old helped set it up and run it) and many books and software for roller coaster design. He also likes to spend hours looking at maps of the different states (we have the DeLorme Gazetteer books) and making up trips to places he'd like to go to (especially the places that have the roller coasters). (And sometimes, we do go!)
12 year olds are SO capable when they set their minds to it. I bought mine a sugaring book and a set of 20 taps and a few cinder blocks this past spring. He tapped 5 maple trees and within a month we had a few quarts of terrific maple syrup!
But no matter what you do, they always get a little bored during the day.
Maybe see if once in a while he likes to have a friend over, or to meet the friend at the park or a public pool if you're going there.
We try to stay home, but kids want to see the world, so once in a while, out we go....sometimes we just take a good road map (or not) and explore new roads together on the way to some mundane errand such as picking up the business mail.
Any of the above suggestions are appropriate to do with the 2 year old in tow, or 'helping'.
Do you think your godson would enjoy an overnight camp sometime? Mine has always gone to overnight canoe camp in Canada...this is his 5th year and he loves it. For three years he went all summer. But this year he decided he wants to see what it's like here in the summer. The next two weeks we are going to try to get out and get to the beach and all now that it's warmed up (an UNDERstatement). We try to go in the morning or in the late afternoon and just stay a couple hours.
Well, hope my ideas help you.
We manage to survive.
Not every day is exciting, but stilll....he seems happy. He accepts boredom when it is here because he knows it will end either by self-action or by me being available to do something.
I know you are watching your Godson but maybe if you need him to specifically watch your 2-year-old while you do chores, you could pay him so nominal amount per hour or for the block of time. I always offer to pay my son if I have a crunch for work, but he usually settles up with a visit to a theme park (or two) or some other treat...he doesn't like to take $ for watching his little brother unless we go out of the house in the evening (which we rarely do). I had a BIG project finished recently, so I still 'owe' him one theme park day-trip this coming week and then later in the summer a visit to the water park. (Well, it's a nice break for me, too, after all that work.) So we have found a way to work as a team so I can get my free time to work and he gets what he wants too but can't give himself without the help of an adult (riding different roller coasters that are nearby).
You can PM me if you want.
Edited to add: I forgot: also trains. Kids of all ages love trains.
But chickens are really truly entertaining.