Don't worry if you can't do everything.
We don't run an agency, but we work with a lot of them. Dialogs Professional Services supports agencies by providing the technical expertise they don't have in-house. We see the inner workings of many ad agencies, design firms, etc. Every agency has a different style or approach to landing new business. Once in a while, an agency partner will be a bit worried that teaming with an outside resource will look bad to a prospect.
Outsourcing technical tasks is a common practice in the interactive business. Smaller agencies and design firms frequently outsource coders and developers. If they had these people on staff, it would be difficult to keep them busy full time. The increase in operating overhead would affect the cost of every project (not just web projects). Large agencies outsource specialized talent for the same reasons. Groups of all sizes occasionally need help when they get overbooked. If a prospect tells you they will only hire an agency that never outsources, that prospect simply needs to be educated about how the world really works.
Outsourcing is a smart business approach. It allows a business to become an expert in a manageable portion of their industry. As a business grows, they can take on a larger portion, but they aren't likely to ever do it all.
When you buy a car, you don't expect the automaker to have made the tires or the glass or the wiring. Your grocer doesn't own farms and ranches. A little closer to home, when a client hires an agency to create a brochure, they expect the agency to have copywriters and graphic designers, but they don't expect them to own printing presses and paper mills.
Agencies need to focus on what brings value to their clients. Successful creative firms understand that there is value in finding good creative solutions, managing projects, and helping clients find new ways to grow their business. The human resources description about who is involved should not be a deal-breaker for the agency or the client.
If you run an agency (of any sort), it's easy to get caught up in trying to give your clients everything they want. The problem is: they don't know the agency business. If you allow your clients to define who you are and what you do, you will not achieve long-term success.
Identify your strengths, define the value of your services, and be who you are. If you have gaps in your capabilities, outsource to trusted, experienced contractors who understand the importance of maintaining your reputation. Be transparent about how you run your business, and let your clients know that you are fully responsible for all members of your team, regardless of whether they get a W-2 or a 1099 and the end of the year. Your clients will respect you for that.