We also lack suitable grandparents (in our case all three currently living are seriously abusive) so we had to go hunting amongst close friends. We considered a variety of factors: how long people had been in our lives, how stable people were, how 'grown up', how likely people were to raise our kids the way we want them raised even if we are dead, and who is financially in a position to not be negatively impacted.
We have first, second, and third choice of homes officially designated in our will. We included a letter to be unofficially part of the custody hearing directed at a future judge explaining the type, kind, and quantity of abuse we went through and why we adamantly do not want our children ever being placed with any biological family member. We detailed why we listed our choices and why we put them in the order we put them in.
Our first choice is one of my closest friends and she has been for about 11 years. She would absolutely in every way do her best to raise my children in a way consistent with my values even if/when they conflict with her own. She has had multiple romantic partnerships where she helped raise their children and she did a smashing job. She is financially very secure and she is getting close enough to retirement that she told me that if she got the kids in about five years she would probably move to working full time for a really long time until the kids were settled because she is pretty set up. I think that would be awesome. The main reason I worry about a judge not picking her is that she is a 'single' (though long-term partnered) lesbian transsexual woman. If I get a super conservative judge they may pass her over despite the fact that she is the best thing since sliced bread.
Our second choice is another super close friend of mine. We were born across the street from one another so there isn't much about me she doesn't know. I love her and trust her to be a good guardian, but she would absolutely raise my kids according to her values and we uhm don't always agree. So she would love my kids and treat them well, but it would not be the life I prefer to envision for them. But she's hetero, married, a CPA, and her husband is a high level employee for Microsoft. They look completely stable and ideal on paper.
Our third choice is my husband's best friend. The only reason he is third choice is because he specifically told us that whereas he would do it if really were necessary he wants to be down the list of options. His wife is awesome and more willing than he is, but they are not yet settled with kids and the idea still makes him nervous. I think they would do a reasonable job anyway.

Once again the kids wouldn't have the life we envision for them, but they would be safe and loved.
So yeah, that's where we went with this.