2-3 times. You should probably donate at least 2-3 times to give them an adequate chance. Sometimes they are split into multiple doses if the count is good enough. I would recommend that you have legal documents drawn up by an attorney. You could be sued for child support at a later time without legal protection and that still may not be enough. You also may want to have visitation rights.
Freeze & quarantine. Dr durso makes good points - donate multiple samples if IUI treatments, 1-2 for ivf. A legal agreement protects all of you, without 1 you could be asked for child support. I would also recommend freezing your sperm and doing fda-approved infectious disease blood tests for you, then quarantining the sperm for 6 months and retesting you for infections. That way there's no risk of hepatitis b, c, hiv.