As soon as I saw this painting technique online, I knew it would be great for my 3 and 5 year old.
(And I gotta admit, I had fun with it too!)

What you’ll need:

Straws
Acrylic or tempura paints, watered down about 50%
Plate, or palette for paints
Thick art paper
Paintbrushes
Painter’s tape
Eye dropper or syringe
Newspaper to cover painting area
(unless you’re lazy like me, since I have a glass table and it’s easy to clean)
First, tape off your page to give it a frame, if you so desire.
Then let your kids paint the entire page with a blend of colors using a paintbrush and watered down paint.
This will be the sky.
My daughter (age 5) wanted to make a pretty evening sky, with pinks and purples. 
So, for her, I let her choose a small picture from the Internet which we printed as her
inspiration picture.

I just let my 3 year old pick out his favorite colors and have at it.
Let this completely dry.
Water down the black or brown paint you’ll be using to blow-paint the tree. 
You will want it to be the consistency of MILK.
You’ll need an eye dropper or a medicine syringe and your straws for this next part.

(These are our colors for the fireworks we did in addition to the trees)
Starting where you’ll want the base of your tree, drip some paint on the page, and begin blowing with the straw to move the paint up, to form the tree.
Continue dripping and blowing paint to make your tree branches go in the direction you want them.
For my kids, I dripped the paint on for them, and they did the blowing.
Also, I was really not prepared for the amount of spit that would pass through my son’s straw and onto his picture. 
Probably could have watered his paint down LESS had I known about THAT.
Anyway, once they’re finished, let them dry, then remove the tape.
Aren’t they just lovely?
Here is Eden’s finished tree:
And Joshua’s spit/tempura masterpiece:

Rather old and spooky, don’t you think?
And, of course, the big baby doesn’t want to be left out of the fun!
Here he is, just doin’ his own thing:
Here is a great youtube tutorial on blow-painting that you may also want to check out.
Hmmm, I think we will
Try these again THIS FALL as well, using autumn colors
as the background/leaves of the tree, then blow-painting the tree in the foreground.
Happy painting, ya’ll!