Enjoying life at any age is the key to having fun , great memories and fewer regrets.
Enjoy the time that you have after retirement, rather than worrying what the children think. They may think you are stranger than ever, but that's okay. Children, no matter their age, think parents are bit on the weird side. And we are.
If you have always wanted to do yoga, do it. They have classes for people with patina. For those of you who don't know about antiques, patina is the shine of age. So, shine. Don't worry about how well you do it, if you must worry, worry about how good you feel doing it.