600K; This a complex question, I believe Harav Chaim Kanievsky discusses a similar dilemma.
I have heard that many shuls who have these type of kiruv gathering with the knowing of the possibility of some people driving there but not immediately addressing it, have a huge success rate within one year of most of their crowd becoming proud Shomerei Shabbos.
You have to understand that for a person who is living a
certain lifestyle and is
a) unaware of the issurim
b) clueless of the reason behind it
c) unaware of the joy and warmth of being religious
d) very hard to drop a certain practice they’re used to and have been doing for ages, in one shot
So I’m not paskening, but telling these clueless people
you “can’t come join us” and feel the warmth, or find out the truth unless you stop doing something you are very used to, don’t even know it’s wrong, or why it’s wrong on the promise of first
give it up everything, then well explain it…
I can see how it could be a struggle and not easy to reach them
this way. Though one has to always ask a Sheilah with a every case specifically as it tends to make a difference when it can be allowed and when it cannot.