There were some school reunions after I had left school, but I wasn't able to attend them because I already had a busy schedule. There were some school reunions after I had left school, but I wasn't able to attend them because I already had a busy schedule.

There were some school reunion after I had left school, but I wasn't able to attend them because I already had a schedulehave been several school reunions since I graduated, but I have been too busy and unable to attend any of them. There have been several school reunions since I graduated, but I have been too busy and unable to attend any of them.

While not perfect, what you have is understandable. I would say it this way.

I can't have metseen my school friends for more than ten years now. I can't have seen my school friends for more than ten years now.

This sentence is fine as is, but the corrected version sounds slightly more natural to me.

I can't have met my school friends for more than tenhaven't seen my friends from school for at least 10 years. I haven't seen my friends from school for at least 10 years.

I think they [are probably/would probably be] unrecognizable now. I think they [are probably/would probably be] unrecognizable now.

"I think they are unrecognizable" implies you've seen how they look now, while the two alternatives imply you haven't seen how they look now, but are guessing or imagining how it might be.

I think they are unrecognizabledon't think I would recognize any of them now. I don't think I would recognize any of them now.