I worry about this a lot. I have 2 boys, ages 5 and 9, no paternal contact.
Although I have male friends, I have found that as we've got older it's not easy to spend time with them. When I was in my 20s and early 30s we all hung out together, went out for drinks with male friends, went to eachother's houses for coffee etc, but once men get married and have kids (and busy lives), hanging out with single female friends in that way just isn't appropriate any more. And as a single mother I find myself being wary of being seen as trying to "steal" people's husbands!
My boys are very close to my Dad, who they see most days and completely adore. But he's getting old, and his football-playing days are numbered I think. I can do lots of boy stuff - I'm not girly at all - we play football, I've taken them to motor racing, battle re-enactments and so on - I'm happy to fulfil all those stereotypically male ideas. But there seems to be something about a man that they need. I think they just know that men view life differently, and that, much as they love me, I won't see things from the same perspective as them. At least, my 9 year old certainly feels this way, as I know he's confided some things in my Dad. He plays football at school too, and enjoys his friendship with the coaches.
But, I do my best, it's all I can do.
My advice would be - don't let this anxiety stop you having a child, but if you have a boy, I think you really need to work on finding male role models. I think that as a lesbian you may actually find it easier to spend time with school dads, because no one will think you have dubious motives!