On a practical, "could you hold this child while I grab a shower" level, it is indescribably wonderful for me to have them so close. But more than that, the way my girls' faces light up when they see their aunts/uncle/grantparents, it means the world to me. The girls have extra arms to cuddle with, friends to play games with, and eyes to watch over and keep them safe. There is pretty much no adequate way to thank them (besides being a world's best aunt for their kids one day. Mom and Dad, I've got nothing on repaying you guys). All kids should be so lucky.
Now, if there was just some way to get all of my extended family in one tiny place.