The ideas I am providing, are about the basic art supplies that you can find easily in any department stores or art supply stores.
Paper: Cold Press watercolor is good for watercolor painting, which got a slight bumpy texture with certain thickness of paper, which the paint with water get easily absorbed to the paper. For Oil color usually canvas is the best. It is challenge to mount and frame canvas board which required lots of skill, so the best option is to buy ready to use canvas board from store.It’s pretty good for both acrylic & oil painting as well. Oil pastels or chalk pastels works good on Bristol paper, construction paper or newsprint paper. Card ideas good with oil pastels.
Paints : Acrylic and Oil color comes in tubes. But for watercolor they come both tubes and blocks. Tubes are more reliable to get the perfect color tone than color blocks.Oil Pastel is very bright and strong colors.It’s really fun to play with oil pastels and chalk pastels.
Brushes: Paintbrush come in a variety of types and sizes. Round ended brush, Flat brush, hard bristles and soft bristles brushes are a few examples. The number on the brushes indicates its thickness. Round ended brush without pointed bristles is good for watercolor.
Paint Thinner/ Turpentine: Both can use to thin oil paints, to get a good flow on canvas. Turpentine does have a higher toxicity rating but turpentine from the art supply store seems to be milder. With paint thinner or turpentine you can even clean your oil color paint brushes. Water itself will work as a wash thinner on water-based paints, acrylics and watercolors.
Palette: You can mix and temporarily store paint colors on a palette. Hand held wooden palette and disposable paper palette are good for oil paint or even acrylic. But for water color plastic palette is convenient.
Other Equipment: Pecil, eraser, Paper Towel or some old cotton cloths, newspaper, glass containers/lids for water or to keep paint thinner/ turpentine and easel
My personal opinion is that never criticize any kids art work. Just we need let them know that we expect their best efforts. It’s that simple to motivate kids and to get their very best to their canvas.