Oh, go for the DS paints, I say. I totally agree about going for the the best possible quality, ESPECIALLY if you don't know how many participants you'll have and may be using the remaining paint yourself. It might as well be what you would buy and use, anyway.
I have simply been pleasantly surprised by the Van Gogh paint and make affordable sets with it for my natural history field study students -- folks who aren't even sure if painting is an endeavor they want to try. I pair the home-made ProArt set with a Pentel water brush and get them all hooked on painting in the field. Muah ha-ha!. :o)