Cavalry may be too good at $4 and too bad at $5. Not sure. It's good that the attack doesn't stack, so draw-to-X engines don't get too crazy.
Is there a reason for Celebration to say "you may"? The situation where you choose not to seems so edge-casey that it doesn't really warrant the additional text. Other than that, I kinda like the card. It's similar-ish to Trading Post, but probably better most of the time.
I'm not sure about EqV. Without other discard, it's worse than Bazaar. With other discard, it quickly get cwazy. There is no space where it's simply decent. I like trivialknot's variant on it, but would suggest Poor House's wording, i.e.
+5$
-1$ per card in your hand, to a minimum of $0.