I would follow your gut instinct on this one. I ahev never really been in this situation so it is hard for me to say YES or NO. In your situation though I would go with what your guts tell you. You know the situation better than anyone else.
Sorry I cant be of any more help
I would keep the conversation light hearted to start with and gradually get deeper. That way, nobody notices the change and it flows more naturally. Always be honest. Dont try to lie or tell half-truths. If this is going to work then you BOTH need to be open and honest but be prepared to hear things that you might not like. As for topics of conversation... the worlds your oyster! There are so many its unbelieveable. Just go with whatever feels natural.
I hope this helps