I'm a single parent and there's never been a father around.
In my experience, tinies don't question it. If you mix in our circles then once you get to 3/4/5, other children will start asking where your Daddy is, since every family has a mummy and a daddy in their experience.
You just tell them No Daddy here, and they learn that not all families have them.
Thrn everything's fine until you hit teen hormones, when everything is always your fault and they wish they'd never been born, but that's just life, and when they come through the other side they remember they have a Mum who loves them so much she chose to have them and would do it all over again tomorrow.
Practically, single parenting when there really is no ex on the scene is different from dealing with co parenting. There are no expectations, so there is no disappointment, and there are no battles over custody or contact, and there's no one else rhe child can play you off against.
There's also no built in babysitter, no extra body turning up to help out at the end of the day, or able to do nursery pick ups etc.
Couples don't fully get the complications, nor do ex-couples. But good friends stay good friends, family is family, and at the end of the day you have a small person and you get to be Mum.
I don't think it's selfish. And I do think doing it now is better than paying to freeze eggs and trying to rebuild fertility later on.