Would you say black is at a disadvantage in queen pawn games or is there a way to equal out the playing field? 

It is a common belief (not a fact!) that white begins the game with a small advantage. If he can convert that to a larger one, he will win. But there are many reputedly drawish openings and equaliser weapons depending on what happens.

If you want a dynamic game (not necessarily equal, but with a lot of potential) then King's Indian, Benoni, Peruvian countergambit...systems like that generally lead to imbalanced games.

For more solid lines, the Slav, Nimzo/QID complex, equalising weapon of many great champions QGD...generally lead to quieter games.

So, it really does depend on your playing ability (if white has a small advantage but neither player is very strong it shouldn't matter that much because there are going to be huge blunders anyway) but I'll suggest that black is a tiny bit worse in all lines.

But not by enough to significantly affect the games of club players (probably matters in GM chess, but I'm not sure)

I recommend playing through the multitudes of Kasparov vs Karpov games that they played for the World Championship.

I think during a queen pawn opening black should not play for equality but for unbalanced positions like king's indian etc. he should try like much as in sicilian defense to steer the game for inbalances, if he try to fight for equality i think yes black is at a small disadvantage.

Baloney.

Look at the history of 1...d5, and see the many, many games won by Black with Pillsbury, Lasker, Rubenstein, and Capablanca handling the Black pieces. 

There is no reason Black needs to seek other openings to get counterplay, only that he needs to play well. 

If he does not play well, no other opening defense will save him, either.