Simplistic low-res Trees

[Geofied]

Hi, my name is Asher, I'm currently working on a low res project that involves making a vast rain-forest which is under deforestation by a construction crew.  I designed a few base trees for the forest, however they are too complicated to fit the current style of the game.  For the final product I'd like the trees to be a lot simpler and only have a pallet of about 3-4 colors (not including outline) per individual color. 

Here are the current trees:



Here's them at 3x size for better viewing:



We're targeting a younger audience for the game, so any tips or help in making these sprites (and the overall style) more simple and appealing to a kids would be a great help.
Thanks!

[Pusty]

Looks good, maybe add another color to the inner trunk at the second picture, not too sure about that tho'

Note: No need to post a 3x version, you can click on images to zoom in (and shift click to zoom out again)