I'm the youngest in my family, and my mom was 39 when she had me. Her mom was 39 when she had her, so my grandmother was already going on 80 when I was born. Therefore I really never got to know her, since she passed away when I was little. My mom is almost 77, and while she was very healthy when she was younger, she's been dealing with a lot of hip issues (replacement, tendons keep tearing) over the last few years. My dad's health has gone downhill over the last 7 or 8 years (he'll be 68 tomorrow). They love to spend time with the boys, but they just couldn't keep up with them when.
On the flip side, my husband's parents were fairly young when they had him (23 or 24), and their parents were young when they had them. So the boys actually got to spend about as much time with their great-grandparents as I did with my grandparents. In fact, my husband's grandfather is 87 and in great health...he's down here visiting all the time.
One of the reasons we chose to have kids 6 months into our marriage instead of waiting a few years was because of my FILs health. His parents both died at young ages and he had already lost a sister. He had a knee injury from college that limited his mobility some what, so we were concerned that heart disease may take him early as well. He has since had a knee replacement and is super active now so our fears were not realized. But I am happy we had them when we did, Dh is older then I am and his parents were a little older when he was born so they are both in their 70s (super active and healthy still, my mil still runs a few miles 3 days a week) But I have to say, my parents are 59 and 60 and they are really enjoying having the grandkids, they went with us to an amusement park last week and my dad was racing the big girls from one roller coaster to the other.
DH will be retiring in 18 years. He will be 51! Isnt that crazy! That is the point where his pension kicks up, and he would basically only be making minimum wage over his pension pay to be a cop, which isnt worth it. Our oldest will be 24. Not sure what he will do at that point. He wants to move to the reserve and live tax free (effectively a raise). I am not so sure of that idea. I think he will want to work for a bit longer, but maybe change jobs at that point. I suspect I will never make my pensionable years as I only plan to go back part time so my retirement will depend more on how much I can shove into an RSP in the next 18 years.
I have to say though, none of that was really a factor in planning when we had kids. My parents have always been financially stable, and then they made some bad choices a few years ago and had to file for bankruptcy. I anticipate they will be living with us in their older years, as they can not afford to stop working. DH's parents are a lot younger than mine, but his dad just found out he might be laid off 3 years before he will start receiving his pension. There are just no guarantees.