I'm not sure what we know now today that I did not know back then when I made that decision. Help me to understand what you think was different then that was not knowable, that's knowable now. Ransom address this somewhat in his answer already.
Having said that, to answer your question, I would counsel them to realize the numerous ethical and moral difficulties that lie ahead of them. Namely, assuming one believes life begins at conception and there are children being created that should not be destroyed, what will be done with those viable (potentially remaining) embryos. If they understood those implications, and they were in a similar context that me and my wife faced as we were approaching statistical aging difficulties, I would give them my blessing.