I’m afraid that the release command “okay” builds up more anticipation and excitement than what’s desirable. I understand the benefits of a release command but in this case maybe it would be better to skip it.
For example, I had two dogs with the same problem. What I did was to send them to their bed whenever someone came to our house. But then they had to stay there for a while. Often they tried to get up and greet the person but if they were too excited they had to go back. Then after a while they would try to go up but this time they were calm. So, I only allowed them to leave their bed if they were acting calm.
Then you need to ask your guests to completely ignore the dogs. They should not talk or even look at the dogs. This can be way harder than what it sounds like. I remember one time when my mom came to visit and I had strictly told her to ignore the dogs but she still, multiple times, looked at them and started talking to them while they tried their hardest to not get up and greet her. Then she got annoyed when her clothes got full of drool and fur. I mean what did she expect 🙃 So be very firm with your visitors, they have to ignore the dogs. They should continue to ignore the dogs even after they are “released”. Let the dogs sniff them and “check them out” without any reaction from the guests. Don’t create any excitement.
If I was expecting someone to come over I sometimes prepared a kong with some food in it and gave it to them just before the guests knocked on the door. The kong was more interesting than the guests and they were occupied for about 10 minutes. By then the anticipation and excitement was way lower because they got distracted by something else.
Having them on a lead could be great to have more control but be sure to decrease the excitement before bringing them to the guests.
But basically I would teach them that it’s only okay to greet the guests if they’re calm. Too excited and they have to stay in the kennel.