If you think it is serious then you should probably tell them. This is part of you, and it is probably better not to try and hide it. I would say take it slowly, explain it to them. Be willing to accept that they might not like it, but equally, if they leave you over it, do you want to go out with them? Don't expect him to take part, don't push it, just go with the flow. You never know, as a furry, he may have come across babyfurs in the past.
So yeah, tell him. Maybe use some of the websites that can be found in the links, they explain it quite well. Just tell him truthfully and take it slowly. I personally wouldn't go for subtle hints. There are some less than savoury sites he could find if he did his own searching - whereas if you explain it yourself that is less likely to happen.
