Spooky or not, snooty jealous trees go back to Snow White and the Wizard of Oz and their jagged lightning bolt limbs and, wrinkled gnarled faces were expressionistic and spooky.
I mean it's sort of surreal enough to cause dismay for us poor mortals at the very least. If you want to lighten the tone, you are going to have to exaggerate the facial expressions such that they look more or less harmless, but with an attitude -- either inept and jealous or noses turned up in mild disdain. Thin line, I know.
Also lightening things up in value might make it less threatening. Deep shadows in a dark enchanted forest are going to trigger primal responses to the dangerous.
You can also keep the warmer colors near the source and cool them as they get more distant. That way it's not all beholding to the values only. What you're really wanting to do is show a difference in tonality to reflect what is going on psychologically.
For the simple value lighting, I would pick a light source -- what? the daisy having the light emanating from it. If so, plot it out accordingly and keep it consistent. And then, if you feel up to it, you can do a little secondary light on the trees -- with a green tinge perhaps to show off their jealousy. . . and/or a little rim light to snazz it up a bit and define the form of the trees if they are getting too dark and lost against the background.
It's a complicated thing, and anything you do is going to push the mood in one particular direction or other. So you may want to get clear on what you want to say and then light it for that mood.
And if you aren't clear on it, then do some research for pics that match where you want to go and borrow some tried and true ideas from that. There are a ton of animated movies that have dramatic lighting, and if you buy, rent or borrow a DVD you can run through it doing some screen grabs for reference that can be analyzed.
Hope this helps.
"Not a bit is wasted and the best is yet to come. . ." -- remembered from a dream