Hi kj.
To be honest, I wouldn't even bother counter-witnessing to them! You will only be wasting your time whilst beefing up theirs!
Think about it - every hour they spend with you, drinking your tea and eating your biscuits, is another hour for them to put on their monthly report slip (form s-8 if memory serves). They can also count you as an RV (return visit) each time they call. And then there's the ubiquitous "placements". Why make it easy for them?
And as for "counter-witnessing" to them, don't forget that these ladies, no matter how nice they seem, want only one thing from you - and that is to see you in a suit with your bum on the seat at the Kingdom Hall.
Remember:
1) They cannot/are not allowed to think for themselves.
2) If you throw something at them that they can't handle, they will merely come back later with Brother Elder, and he's a very different animal! Before you know it, even more of your precious time will be wasted in futile and pointless discussion with a closed-minded drone!
3) Free and open debate has never been nor ever will be on the agenda for JW's.
4) Noble though it is to want to liberate these people, it is not possible to do so, because the vast majority of them are actually happy in their ignorance.
Take it from me friend, if it's not too late, don't bother with the two nice ladies. Give them their mags back. You don't have to be rude of course, but seriously, don't waste your time!
Believe me, I know - I once was "Brother Elder/closed minded drone" and I could be very persuasive! I was so persuasive, I even believed what I was saying myself! Please, do not put yourself in a position where your time can be wasted and your liberty put at risk!
Jonty