At least in a public place that would be OK to some extent:

• in an Islamic country greeting and what we may call necessary part of a conversation would be permissible. For example if it's a business lunch or dinner a conversation about the business would be necessary. If it's just a lunch between friends, i can't imagine that in any so called Islamic countries to be possible or considered as permissible and I'm not sure whether it is due to religion (of course shari'a rules apply and have an effect and they don't allow gatherings between female and male who are not mahram unless some conditions are fulfilled) or local customs.
• But as you seem to ask about a situation in a non-Muslim country one should take into account the local customs and what is more likely to be regarded as polite or impolite. For example you may know that a Muslim is asked to accept invitations. And on the other hand it could be a kind of da'wa (invitation) to Islam as "intention" play a big role in our religion. But in any case i wouldn't recommend any husband doing this without the knowledge and accordance of his wife. And i even would recommend him to consider insisting that his wife would be present and come along as often as he can. If this wouldn't be possible he should even consider stopping these kinds of gatherings, because he would play with fire.

But i think if the wife dislike such things she should tell him, as it's a problem that can be solved by conversation. An appropriate Islamic POV is secondary here.

And Allah knows best!

At least in a public place that would be OK to some extent:

• in an Islamic country greeting and what we may call necessary part of a conversation would be permissible. For example if it's a business lunch or dinner a conversation about the business would be necessary. If it's just a lunch between friends, i can't imagine that in any so called Islamic countries to be possible or considered as permissible and I'm not sure whether it is due to religion (of course shari'a rules apply and have an effect and they don't allow gatherings between female and male who are not mahram unless some conditions are fulfilled) or local customs.
• But as you seem to ask about a situation in a non-Muslim country one should take into account the local customs and what is more likely to be regarded as polite or impolite. For example you may know that a Muslim is asked to accept invitations. And on the other hand it could be a kind of da'wa (invitation) to Islam as "intention" play a big role in our religion. But in any case i wouldn't recommend any husband doing this without the knowledge and accordance of his wife. And i even would recommend him to consider insisting that his wife would be present and come along as often as he can. If this wouldn't be possible he should even consider stopping these kinds of gatherings, because he would play with fire.

But i think if the wife dislike such things she should tell him, as it's a problem that can be solved by conversation. An appropriate Islamic POV is secondary here.

And Allah knows best!