I always play 4.d4. I don't see how this mitigates the KG's fun aspect.
The line that takes the fun out of the King's Gambit
 
    
  
  
  If 4...exf4 (though, to me, 4...exd4 seems better) then I like to play 5.Bxf4. If Black then plays 5...Qxe4+, 6.Qe2 is ok. 5. Nc3 looks decent enough though.
Against 3...Qe7, some people like to play the simple 4. fxe5. I guess it's all a matter of taste.
 
    
  
  
  Instead of the queen comin down,Ive had a lot of players lately bringing their black bishop down,and I have yet learned how to properly defend it,and develop
 
    
  
  
  The line in the Cunningham Defense is one of my favorites as white. After:
Black has to be very careful.
Here' Morphy playing that line vs HE Bird (Morphy was playing 5 masters simultaneously)-
Here's Morphy playing a different line against a weaker player, Judge McConnell:
see also: http://www.chess.com/groups/forumview/kga---the-cunningham-defense?lc=1
 
     
     
      
What do you recommend against Keene's line: