Applicants on the buy-side typically take one of three approaches:
1) I'm a numbers guy, love portfolio theory and want to run my own fund one day. I'm going to business school to delve deeper into finance, build my network and transition into a position that is better aligned with my career goals.
2) I'm an industry guy. I covered one specific industry and now I want to jump in. I need b-school to make the transition.
3) I'm a people guy. I loved the person-to-person interactions on the buy-side. Having discussions, having people sell me and selling people. I want to build on these skills and transition into an area like private wealth.
Sounds like you fall into category 3. I've seen people successfully spin this in addition to saying they want to focus on the athelete market. Sounds like you have your story lined up pretty well. I wouldn't worry about the boutique nature of your firm. In many cases that can actually be an advantage because of you probably have had more responsibility than your peers at larger firms.
If you really want PWM, keep plugging away at CFA -- even after you get into b-school.