I'm sure your aware that there is a market for your old barn boards.
Depending on the width (wider is prized) anywhere from $3.00 +/- LF on up to say $4.00 +/- a LF
I just removed a slab myslef, however it was only 14X20 and a rented jackhammer, prybar, trailer and hard-labor I hauled it off to the city dump myself at $54 a ton.
If I were to remove a larger slab, I would rent a small front end loader and do it that way. I would imagine you could get a crew in to do it for you, but your probably wanting to save $$$.
What I would do is this:
1) find out how much the dump charges per ton (you can fairly easily calculate how many tons you have)
1a) rental of a loader/trailer and gas (how far is it to the dump)
2) Find out how much to have it done
2a) some outfits will even drop a large dumpster on your property, you fill it they haul it (for a fee of course)
3) factor in your time and what it is worth
and then see what of the 3 options appeals to you best.
I don't think burying it on your property is a good option. But, could you make some sort of small rubble fence row with it or something (once again I don't know the legality or environmental aspects involved).
I'm just throwing out all the ideas that come to my mind.
"Go as far as you can see; when you get there, you'll be able to see farther."