Nice weather here. Low 70s for a high. Today DH & I will be spending time with DD and her family plus the family of one of her besties. We know their close friends quite well - their children even call us Grandma & Grandpa! So it will surely be a very pleasant day indeed.
Not only bad things apply with the old expression, "What goes around, comes around." While growing up, our children were close to many of our friends and were comfortable around them, even adults without children or whose children were grown. These days, we're close to many of our children's friends, and are comfortable around them.
Some of our friendships of various generations are formed during our large holiday parties (with children of all ages welcome). We invite neighbors, young and old, and encourage our children to invite their friends and sometimes their friends' parents. Other relationships, now 25+ years standing, started when our kids were teens and we opened our house to their friends. Some of these these 40-ish "kids" stay in closer touch with us than with our children.
My mom had friends of widely different ages so this feels very natural to me. Friends of any/every age are blessings in our lives.