The problems I foresee are threefold:
1. Kids tend to believe that an absent parent is absent because that parent does not love the child and therefore that the child is bad and unloveable.
This is a kind of default position, and you will, in my opinion, need a good explanation of why the child has no contact with the father and his family that does not unduly demonize them...and be ready to discuss this with your child very often. I would also advise that you have some GOOD things to say about the father (I presume there must be good things, because you had some sort of connection to this guy, right?)
2. If you demonise them, the child knows that it carries those genes, and kids are often fearful that they will be just like a despised parent.
3. Come adolescence, when you become the dumbest and least desirable thing on earth (
for a few years ) the absent parent often becomes a beacon of desirability and perfection, and the kid believes that life would be all joy and understanding if only they could go and live with the absent parent. The less expreience the kid has had of the clay feet of said absent parent, the more it is possible for said kid to give them all the most desirable attributes of the perfect parent.