I'm a no BS guy so I'm gonna give you a no BS answer. I HONESTLY think it would be a hard sell, BUT I'm not a tennis fanatic. The first thing that comes to my mind is that it's big. So a potential buyer is thinking, "how am I gonna get that in my car and how long is it going to take to set up?" It also looks like it's really only for little kids so a potential buyer is thinking how much use are they going to get out of it. Also, is there even a large enough market for youth tennis? I have NO idea. Tiger really catapulted youth golf but I doubt tennis is as large.
As far as price, only you can figure that out. Figure out how much it costs to build one of them and then you also have to recover all other costs such as patent expense, etc. I've heard patent's are very expensive so you would probably have to sell a BUNCH of them to break even.
Good luck with your business. I'm not trying to be a dick and ruin your dream. Just an honest opinion. You MAY want to join a golf forum (like you mentioned) to get better opinions. Once again, good luck and in a few years bump this thread and let everyone know that I'm an idiot for being wrong.