First of all, you don't "come out" as a furry. It's just a hobby, there's no need to take it that seriously.
Secondly, you shouldn't buy a suit until you stop growing. Trust me, eventually your going to grow out of it and 5k is down the drain.
Third of all, just explain that you take an interest in animals with human features, that's really it. If they say it's a weird hobby that's fine, it is. But that's okay. If they don't want you to continue being a furry just ignore them. It's whatever, and if you don't have any malicious intent then you can trust yourself to continue doing what you.