Which fish oils do you give kiddos? (and more on constipation)

I'm not as good a mom as lots of you, so haven't been forcing the fish oils as a few I've tried (for kids, all flavored, some in gummy form) have been rejected thoroughly. Now I'm taking Mr. A (the one with constipation) to an acupuncturist who has advised (among other things), cod liver oil. So far have been giving him a tiny amount in a spoonful of yogurt and tried yesterday with the other 2 as well. They took it because I sort of sneaked up on them, but I doubt this is sustainable! So, if there's a brand you use your kids don't hate, let me know!

After about a week of nice, soft poops, we're back to same old same old hardish and dry with holding (encopresis). I am sooooo mentally wiped out as he is always on a regime of some kind for this which requires my keeping track of everything he eats, drinks, all the other stuff (flax, psyllium, etc), time and quality of poops, etc. You should see my little poop journal for him! All day I'm thinking of what to give him, when, and how. We first the peds' recommendations (we tried this for a long time with little success) and now the acu's (which seemed to work the first week but no longer working and 5 days without a real poop).

His brother eats the same diet (minus the stuff to help with pooping!) and his poops are super soft and mushy all the time. Never a single hard poop in 2 1/2 years...help!