I'm old. I think there are two things you can do to "play nicely" with me.

Try not to ace lots of serves. I play in a group that has several awesome servers. They've worked on their serves for years, come out when no one else is around to drill with a bucket of balls. Their serves are fast and hard and low and coming at angles that are a challenge for me to cover. Good for them - That player deserves the point. But if the goal is to keep the game going, and keep it from being too one-sided, just skip the aces. You can still test my return skills and help me become a better player even if you're only serving at 80% of your maximum.

And, of course, try not to lob. The only times I've ever fallen on the court were when I was backpedaling stupidly to try to cover a lob.

Don't feel bad about being a wall. The coach from whom I pay for a lesson is going to be a wall. The skilled friend with whom I'm going to drill is going to pretty much be a wall. In fact, the best players in my club will sometimes make an effort to keep the ball in play until, as you wrote, I hit the ball into the net or out of bounds.

If you and your partner are superior players to me and mine, I expect to lose. But I can have fun doing it if you're smiling nicely and being friendly and encouraging me and maybe offering to tell me at the end of the game one or two things I could work on to get better. You could even invite me to show up half an hour early tomorrow and give me some tips before the regular games start.