Some people will say that it loops and a baby toe can get caught. I have never ever had that happen with Monopoly. And you can iron polyester - it was the older invisible nylon thread that sometimes melted.
Having said that, Monopoly is a little tricky to work with, you have to loosen your tension wayyy up.
And having said that, personally I would just pick a dominant color in the quilt and use that. If you don't want the quilting to show as much, use a finer thread like Bottom Line, which is 60 wt, or Microquilter, which is 100 wt. I'm currently using Microquilter on a memory quilt I made from my grandfather's Hawaiian shirts. I definitely wanted the focus to be on the shirt prints and not on the quilting. It's quilting up beautifully.