I have two males...my mom absolutely did not want a male dog...at all, much for the same reasons as your mom. The biggest thing of course was the marking, she was really skeptical but finally gave in and let me get Micki. The first day he was home my mom was sitting on the couch, Micki came running down, went right to her and lifted his leg Not good, lol. But, he has never done it since, he was neutered around 6 months and Jack still doesn't even lift his leg outside yet, he was neutered at about 2 months (the shelter did it). I will say that when we are out on walks and things, my girls mark much much more than my boys.

Good luck!