fotheringhay I understand where you're coming from. I'm a single parent and all my family are dead with the exception of my DSis (who lives abroad) and a few elderly aunts. I have a very small 'safety net' and I frequently wish my children had more loving adults involved in their lives. I identify with you there.
My X was abusive, which is why I left him shortly after my DTs were born. He is only allowed supervised contact so my DC's relationship with him is superficial to say the least. If my happily married and very loving parents were still alive it would add a special dimension to my DC's lives and relieve some of my concerns, but even without them my DC will still be fine.
That proves two things - the Children's Society point about the number and quality of relationships having more effect rather than the biological parent bit (my Ps being much more supportive than the father), and that while extra support can enhance things and lack of support can make things more difficult (which is basically common sense), none of these necessarily affect the outcome for the child. I love my DC, I care passionately about their welfare, education and life experiences and do my best to maximise these. There are parents who do more and parents who do less than me, and whether or not they are single or married to the father of their child won't make a bit of difference to the value they put on their child's welfare as that's down to them as individuals.
I see the sense in bigger family groups (which I would extend to include long-term family friends BTW), but I don't see that they necessarily have to include the father. The father is certainly a logical assumption because he provides one half of the genetic material that created the child, but in terms of stability, love, support, guidance and nurturing, any adult can provide those, so the absence of a father if one neither exists or isn't suitable for whatever reason, is neither here nor there IMO.
To come back to the point made by fabulousdarling I think it's a false dichotomy to equate the lack of a father in the child's life with being completely ignorant about that side of the child's heritage. In the case of modern sperm donors, it is now common for complete medical background to be taken and for a history of the donor's likes, dislikes, hobbies, interests, work experience, etc. to be provided. Obviously it is anonymous, but you only have to look at some of the posts on MN to realise how much of a picture you can build up of an anonymous person.