for singleplayer i usually use keys that close to WASD like E,Q,R,F. for 2nd player you can use numpad (if you have one), there is no space key for this player, but i think jump is okay with W, just remove hit from space, so if the player accidentally press it, he won't have to wait until the chop end.
So the best way is just make a control settings menu so players can themselves choose the best. But here is good standart
1st player:
A,D - move
W -jump
R - chop
2nd player:
NUM_PAD4, NUM_PAD6 - move
NUM_PAD8 - jump
NUM_PAD7 - chop
