Jean,
I love the MDF panels with the acrylic gesso, but you don't really need to use a gesso first unless you want a white underlayer. You can use it directly. I tint mine a little bit then I get a large single action Badger airbrush and spray it with Goldens fluid matte
acrylic colors. It makes a fabulous velvety flat surface .
Not all stores carry the matte fluid but the
www.italianartstore.com
does. I use the airbrush extender with it. The large airbrush is about $100 and the I use an inexpensive Sears compressor to attach it to. It is like having your own custom spray cans and easy to do.
I think the subject is charming, but before you start ANY composition you have to consider the color harmonies. If this a complementary scheme with the very pink face of the child, then perhaps the jacket should be a greener black than it is and the table a red rather than a yellow brown.
I aways work out my color harmonies before I start so I know where I am going. Before I paint or photograph a subject I make sure that the outfit resonates or harmonizes with the background.