A.E.
We were in a similar boat. My parents are in their 70's but very close to our kids, and my husband's parents are in their 60's but far away and not as close emotionally to the kids. Both of our sisters are unmarried, so we looked at our friends. We spent about 2 years deciding, and ended up chosing dear friends of ours who also have two kids, who we spend a lot with and who our kids adore. (The 3 year old calls them 'aunt and uncle' already.) We told my parents, and my mom understood - but it took some time with my dad. (My husband's family was fine with it. ) My sister would be upset, but she couldn't handle raising them on her own, and frankly, i feel i have more in common with my friends than her. So we chose not to tell her. If she or my sister in law get married and we love their husbands and the way they live their lives, we decided we could always change custody to them later.
Back to not chosing our parents: we decided that our kids will always have that special bond with their grandparents, but it would be important for them to feel like they had parents (not to mention "siblings") as well. I mean, how shattering would it be to lose your grandparents, who were like parents to you, as a child or as a teen? When i explained this to my dad, i think it made him realize he was being selfish. And besides, looking at the practical side: he and my mom get pooped now from a few hours of babysitting a toddler and an infant, so how could they tote 2 boys to baseball games in 10 years time?
But what it came down to chosing friends we had to think about a couple who had similar values as us, and would expose our kids to the same things in life we will expose our kids to. I think that's important to think about. I hope this helps. Feel free to write me back if you want more thoughts. Good luck - i know it's not easy!