Try to establish a play, eat, sleep routine.

It's pretty normal for cats to get hyper around mealtimes or when they're hungry, which is a likely explanation for why the incidents tend to happen when they do. Therefore, I think it would help you to change when your play sessions happen to right before mealtimes. In the wild, the natural pattern is hunt, eat, then sleep, so if you can establish a routine like that, hopefully it will encourage the younger cats to be diverted from bothering the older cat while you're playing attention to them, and to sleep when you're not.

Arrange your furniture to help your older cat avoid them.

Use your existing furniture and new cat furniture to create alternate routes throughout your house. Make sure these alternate routes have multiple ways they can be accessed, so no cats can be trapped up in furniture by the others as they wait for it to come down. The idea is make it so your older cat can simply avoid your younger cats by going up on this furniture. If done right, it can avoid these incidents on its own.

Look for and fix any problem areas.

There may be areas of your house where incidents particularly happen. For example, there might be a chair the cats love to hide under and wait for their victim, so they can ambush it. Or maybe they tend to guard a shared resource, like the litterbox. So start taking notes of where these incidents tend to happen, and if you notice a problem area, try to think of ways to get rid of it. Add more of any resources that are being guarded, block access to hiding places that they use for ambushing, and make alternate routes with cat furniture.

Try to establish a play, eat, sleep routine.

It's pretty normal for cats to get hyper around mealtimes or when they're hungry, which is a likely explanation for why the incidents tend to happen when they do. Therefore, I think it would help you to change when your play sessions happen to right before mealtimes. In the wild, the natural pattern is hunt, eat, then sleep, so if you can establish a routine like that, hopefully it will encourage the younger cats to be diverted from bothering the older cat while you're playing attention to them, and to sleep when you're not.

Arrange your furniture to help your older cat avoid them.

Use your existing furniture and new cat furniture to create alternate routes throughout your house. Make sure these alternate routes have multiple ways they can be accessed, so no cats can be trapped up on furniture by the others as they wait for it to come down. The idea is make it so your older cat can simply avoid your younger cats by going up on this furniture. If done right, it can avoid these incidents on its own.

Look for and fix any problem areas.

There may be areas of your house where incidents particularly happen. For example, there might be a chair the cats love to hide under and wait for their victim, so they can ambush it. Or maybe they tend to guard a shared resource, like the litterbox. So start taking notes of where these incidents tend to happen, and if you notice a problem area, try to think of ways to get rid of it. Add more of any resources that are being guarded, block access to hiding places that they use for ambushing, and make alternate routes with cat furniture.