The standard approach to sex is rather like a three course meal, it proceeds in set stages: you kiss a bit, fondle a bit (maybe give her an orgasm), then have vigorous intercourse until he comes. The End.
It’s not a bad model for sex, but it’s limited, and can get pretty boring over time.
I suggest you take a less lineal approach to sex and think of it less like a three-course meal and more like a picnic. At a picnic everything is available in front of you and you can pick and choose whatever you want, in whatever quantity, at whatever pace, and in whatever order you please.
It’s the same with sex: you can do whatever you like, in whatever order you like, at whatever pace you like, in whatever quantities you like. You can intersperse bouts of intercourse with bouts of oral or other genital stimulation. You can stop and have a cup of tea and chat before resuming; you can get up and have a dance; you can read some erotica to each other; you don’t have to have intercourse; you don’t have to have an orgasm; you can stay in orgasmic states; you don’t have to stop when he comes - he doesn’t even have to come.
In this way your lovemaking ebbs and flows, with peaks and valleys. You get into a gorgeous flow of experience. There may be orgasms or there might not, it doesn’t matter, it’s not about orgasm it’s about sharing pleasure. You may find yourselves in states of extraordinarily high arousal, better than orgasm, you may even find yourselves in altered states of consciousness.
You both let go into the experience. One may naturally be the leader, more commanding, and the other more receptive, more yielding - if that’s how your eroticism works. Or you might flow from one approach to the other seamlessly, if that’s how it goes for you.
There is no ‘right’ way or ‘wrong’ way of making love in this model. It’s simply whatever evolves for that couple at that point in time.
With this approach the age or physical capability of the couple doesn’t matter. All you need is the ability to connect and flow with the moment.
For modern couples - more used to sex as being a process and a performance - this is a radically different approach. It might feel weird at first, but over time you’ll get better and better at letting yourselves go and proceeding in any way that feels just right, for you.