Probably the best thing to do here would be to write 2 modules, one a direct port of the C api (so people who know the API already don't have to learn how yours works, but can access the module from perl) and then another module that wraps the low level calls with the API you prefer.

At the very least, if you get the OO interface 'wrong' someone can use your base module to make a different interface.

I think the key point I'm trying to make here is that if someone knows the C API for the library you are making available to Perl it should be easy for them to start using your module as well, preferably with as few unexpected changes as possible