That is wonderful that you are going to get him some friends. Just make sure you will be able to bring them back in case they do not get along. He sounds like he may not be grieving any more. Sometimes they recover quickly.
They should be fine in that cage for now. The baby boys will be small. But remember, you have to quarantine the baby boys from him for at the very least a week. You will need to see if they develop any illnesses like respiratory infections. And they can not have play dates during this time.
I have found that my males are more accepting of other males than my females are of other females. Beaker had to live with his seven boys for a few weeks until they had their homes. He didn’t mind them at all. I tried moving the cages around and he lived with Spartacus for a while and loved him. Then I had to move things back and he had his two left over boys back. I then introduced him to a Lotus and he loved him. He protects Lotus when his boys get too rough with him. I think you will do a lot better introducing him to two baby boys than you would to an older male.
Like I said, make sure you can bring them back in case they are not right for him. Some rats just do not like each other. You may get it on the first shot or you may have to try a couple times. This is more for him than for you, so make sure he is happy with his new cage mates.