You’re right, zaff. We are allowed attend services in other churches, as long as we also attend Mass, now. But, when I was a kid, we weren’t even allowed to step inside of another church, at all. Just visiting another church, talking to the minister, or talking to the people in a nonreligious social gathering, is probably not too much of a problem, at least not for an adult. Even for a teen that is accompanied by a responsible Catholic adult that can answer any questions they might have, it’s probably OK. Anything more that, tends to make me a little more uncomfortable.
As Catholics, we should certainly never partake in any kind of communion service with members of another faith. I, personally, have had a very profound experience that convinced me of that. It’s one thing that I’m very sure about. For teens or younger children, I would not be comfortable having them participate in a social situation, especially where there might also be some sort of preaching, or discussion of any differences between beliefs. Maybe some people will think I’m being too “old fashioned”, but I do tend to use more caution when it comes to matters that can seriously affect our own, or our children’s faith.