You could just as easily frame up the courses with 2 x 4s and plywood as the deck subfloor. I'll detail the construction in the following steps.
Step 1: Materials
2x4s Pressure treated (unless you have 3 swimming pools panels laying around)
4x4s Pressure Treated
3 4 foot by 8 foot 1/2 plywood
Metal Kid's slide
4 inch diameter PVC pipe
2 inch diameter PVC if you want to have a course lower to putt down too
3/4 inch plywood
We had quite a few things laying around the house. The biggest expense was the indoor/outdoor carpet. We spent about $150 U.S. dollars in 2010 to build this.