My DD is in HS and we did our first guesting at U11. At first within the club and then as she got older, we guest played with a few other clubs. We found it highly valuable in the early years but not as much anymore as she's on a highly competitive team and the opportunity for injury doesn't seem worth the risk.
have your coaches been OK with it?
All of her coaches have been totally fine with her guest playing within the club. Guesting with another club? I would say that they all frowned on it generally, but most of them were ok if the club in question was located far away. Clearly, this is because they are worried that your kid is being recruited away from them, and only approved guesting if the club wasn't a realistic option for us to jump ship to. Even then, they would always mention the possibility of injury, especially if we had a tournament or games coming up ourselves. Her coaches were most supportive of her guest playing at another club if: a. It was not a direct competitor in their geography. b. Our team was in a dark or slow period as far as games. c. There was some compelling opportunity for her (guesting at Surf Cup or Players in Las Vegas) that she couldn't get on her team/club. In those cases, we could convince the coach to endorse it, even if they didn't like the idea much.
The big thing about guest playing as a keeper is mentality and confidence. I had to talk her into it most of the time. She can be a creature of habit and forcing her out of her comfort zone was something we as parents tried to do in order to get her to come out of her shell and learn. It was hard on her initially, but each time that it worked out well, she would gain more and more self-confidence.
My kid was a lot like yours in the beginning. She liked her first club and didn't want to play for anyone else. But her club fired her coach and when another coach in her club passed her over for a kid from another club, she learned very quickly that "loyalty" means nothing in the club soccer game. After that experience, she understood the value of guest playing - even if you're happy with your current coach and club, making connections with other coaches and players will create opportunities down the road that really can pay off. The team/club she ended up with (and hopefully will finish out her youth soccer career with) was a team she guest played for once several seasons before actually joining them. We stayed in touch with the coach and guested a couple times over the years and when she was finally ready to make the leap to a higher level team, they were in need, and it worked out perfectly for both sides. When she had first guest played with them, she had actually been referred to the opportunity through another coach that she had guest played for at a different time. If it weren't for getting out there and seeking guest playing opportunities, she wouldn't be where she is, and wouldn't be getting the recruitment opportunities she currently has. In our case, networking really paid off in the end.