I understand being reluctant to pull the cylinder head. It really isn't that bad of a job and could give you and your son some under hood time together if you decide to tackle it. When I was in your shoes this is the path that I took for what it is worth.
If you want to try to extract the broken bolts on the car, I would recommend removing the exhaust manifold so you can see where the bolts are snapped and if there is any thread remaining outside of the block. You will need to replace the exhaust manifold gasket either way so the manifold will need to come loose regardless. Don't be surprised if you break other bolts in trying to remove the manifold. Use lots of penetrating oil, PB-Blaster, or whatever you prefer before trying to loosen the remaining intact bolts to minimize the chance of them breaking. Putting heat on them from a propane torch will also help, but be extremely careful about fire and fuel being in such close quarters.
For the broken bolts that remain, if there is any thread visible outside of the block the easiest thing to do is to thread a nut onto whatever threads you can and weld it to the stud. Then follow the same procedure with removing the intact bolts. For the bolts that are broken off flush, you will either have to try to weld a nut on flush with the block or drill them out. Again, use lots of penetrating oil, heat etc. I the key is to drill straight and slow. I would not recommend using a bolt extractor or "easy out". They are made of hardened steel which makes them inherently brittle. If you break the tool in the stuck bolt you will be in a world of hurt trying to drill through the broken tool. Ask me how I know. By the time that you buy the hardened drill bits, extractors, and chemicals, the $8.00 to $10.00 per broken bolt that the machine shop will charge to remove them for you will seem really cheap, not to mention the time and frustration.
Just my 2 cents.
Kevin