Hi There ^.^
Telling them your a furry is easy, cos the chance of them knowing what a furry is, is next to nill.
My mum is of the church going type and I had no intentions of telling her anytime soon. but after spending the Xmas Holidays with her, she found my Fox tail and ears snooping in my room and she quized me, so i caved in but only told her a watered down version of it.
I showed her some clean furry art and said that it was a group of people, mainly online that love anthropomorphic animals, fantasy, cartoons, art, gaming, music, storys, roleplay and that some even dress up in Fursuits to roleplay in.
I never told her that its full of Gay's and Bi's in furry that love to get together and get drunk now and then, or that i too would love one of those sexy cool fursuits.
as this im sure would mean a crack over the head with a cross from her, screeming "convert now demon" :P
Furries, are little known here in NZ so it makes telling older people easy'er.
Its nowhere near the same level as saying you Gay, Bi or whatever, as they know what THAT is.
You dont need to tell them anyway. and any age that your comfortable with who you are is a good time if you do decide to say.
Have a great day, my friend ^.^