I think you need to reinvent yourself, or at least find the person you would have been if the conformity and motherhood thing hadn't happened.
At around 40 i suddenly realised i was dressing for other people, suits and blouses and pearl earrings, nice dress and smart shoes, haircut every 10 weeks, boring makeup. That's not me, it's what was expected for my job and bringing up children, which is fine and i don't resent it, but i don't have to do it anymore. It's funny that how you dress can actually affect how you behave and how you feel about yourself. Now i wear much more casual clothes, have birds nest hair that i don't cut, and funky makeup. I feel much more like myself, and i now do more of the things that i used to like; mountain biking, music concerts, city breaks for exploring. It's how i used to be before my best friend died and i started a family.
On the "uncomplicated fun" part, i have been getting noticed by men, i'm suddenly aware of the second looks, and men talk to me (sometimes women too), the kind of men i like. I love the occasional flirt (not gross throwing myself at guys and making innuendos, just actual conversations and making a connection). I'm not interested in casual sex though, it's never good, it's just nice to finally feel seen as me, and to be understood as an indivdual - not in relation to a role i do.