Focus on what the charity work prevents you from doing. There is nothing wrong with seeking personal growth. You want a full time job, and you want a career. You want to acquire knowledge and experience that the charity work is not allowing you to pursue. Focus on the non-monetary aspects that the charity work cannot fulfill. Most importantly, for your own sake, figure out a long term goal, something that a full time job will be a major and required step towards achieving. Once you have all of this clear for yourself, then your ready to discuss it with those you care about.
I've had several career changes, and left great cities and amazing living situations to pursue my career, in various ways that my parents and some friends have not understood. Often when people judge or question your decision, its simply because they only know their own perspective and don't know why you are making the choice you are. Empower them to empathize by sharing whatever is motivating you to want the change. Even if on the surface it mostly seems like it's monetary, there's a reason you want to have more wealth, so you can think through and explain that part too.
When you broach the subject after thinking through the path you want to take, start off with the things you want, then why you don't see the current charity work as being able to fulfill them (or fulfill them quickly enough), then explain how you plan to fulfill those things with your new path. This always falls under the old idea of "ethos, pathos, logos" where when speaking to an audience, you first have to establish the context, then align your audience emotionally with what you want to say, and now you can present logic.
For example:
"Your child has cancer"
"I have some bad news"
"I'm a doctor, and I've run some tests"
Is the reverse order of what we would expect, but these are the pieces of information that need to be presented.
Following proper order:
Ethos: "I'm a doctor, and I've run some tests"
Pathos: "I have some bad news"
Logos: "Your child has cancer"
In your case:
Ethos: "I've been thinking really hard about what I need for my own
personal growth"
Pathos: "The work we do is important, and I do
want to continue"
Logos: "I really want to _____, so that I can
_____, in order to _____. And that is why I want to work on becoming/doing
_____"
These phrases specifically aren't great or very specific, but hopefully get across the idea of how you want to structure when you discuss the change in your work/career. You can also work on figuring out how to phrase your starting statements in a way that gets people to say yes or generally agree with you. Such as "Shouldn't everyone spend time discovering their own potential?" etc.
