Hey Darlene,
Congratulations on narrowing your niche and getting SO specific!!

It's awesome that you enjoy working with non-profits and it seems like you are really close to the animal welfare niche. If that's who you want to play with, then narrow it down!!
I just read the book "The Dip" by Seth Godin and Shari touched on one of his important points. Narrowing it down makes you the Go-To person for that niche. You will become an expert. Seth (as if he's my buddy LOL!) says
"Scarcity makes being at the top worth something." I look at a very narrow niche as "scarcity." Every VA has their specialty. What makes one different from the other is how unique they are. A lot of VA's market themselves to non-profits (I can think of 3 off-hand), but how many market to animal welfare and service organizations?! I'd be surprised if you wouldn't be the first one.
When I started, I was a VA for Coaches and Small Business owners. I quickly found that I wanted to work ONLY with Coaches. The moment I refocused all my marketing to Coaches, I started getting more Clients. Now, there isn't an intro. session that goes by where someone doesn't say (with surprise in their voice)...
"You ONLY work with Coaches?"
I know there are many stories out there like mine. I truly believe that narrow is better. Trust your gut! Play with where you want to play! In the end, you'll come out on top!
Create a great day!
Kristen
Just my thoughts