I like each of he DTs you mentioned (especially Melton), and none of the DEs you mentioned. Certainly Avril and Osi are above average pass rushers, but unless the market is dry -doubtful- there going to want more money than they're worth.
Avril is probably going to be the safest out of all those three DEs.
With Osi and Freeney, the reason why I think we might be able to sign either of them to a (relatively) cheap short-term deal is because of their age (31 and 33) and the fact that both of them struggled to produce this season.
I think Freeney still has enough speed, and the spin movies, to put good pressure on the QB from the DE position. The Colts switching defensive schemes and turning him into a 3-4 LB didn't play to his strengths, and I think that played a big part in his struggles, as well as playing hurt.
With Osi, I think the fact that the Giants defensive line in general all struggled this season, and the fact that he rotates in with Jason Pierre-Paul and Justin Tuck (who both didn't perform as expected) hurt his production. But I think he still has juice left in the tank.