Freeman and Heyward are in slightly different situations due to Heyward being a year ahead.
My guess is Heyward will get $5M and $9M his last two arb years. After that I think it is unrealistic to think in terms of anything below $15M AAV and quite possibly unrealistic to think in terms of anything below $20M AAV. Adam Jones for example is averaging $15M for the post arb years of his contract and isn't as good as Heyward, was older at time of signing. Add in inflation and I think it is clear the Adam Jones deal represents an absolute floor on what Heyward should get. In fact if Heyward signs for something like the Adam Jones deal, his agent should probably be sued for malpractice.
For Freeman, my guess is he will make $4M, $7M and $10M for his arb years. As I expressed earlier, I suspect he can expect to do better than Fielder if he hits free agency. If he decides to sign earlier he will obviously take less because of the reduced risk. But like Heyward, $15M/year for the pos arb years represents an absolute floor in my opinion.