Kneeling push-ups are fine, unless you have a goal of doing unmodified push-ups.
You’ll want to be sure your clients are training the push-up from a long lever position as this has a more accurate carry over into unmodified push-ups.
Inside The Barbell Collective, I encourage hands-elevated pushups and using surface height as the thing we progress until the client is ready for long lever push-ups from the ground. Most commonly, the TBC programming omits push-ups from any of the conditioning portion of the workout so that clients don’t get sloppy in their form when they’re tired. So push-ups are programmed as a strength portion of the workout *most often*
You can begin hands elevated and then progress to a banded push-up like shown here and then progress by using thinner bands over time.
Obviously the progression of the program matters too! Other things that can help your push-ups are: slow eccentric push-ups & hand release push-ups. Depending on you/your clients, you might consider keeping reps low to keep quality high. Programming 20 push-ups where 3 are solid and the remaining 17 are sloppy isn’t all too helpful.
In many cases, quality begs quantity. So start with quality and go from there.