Shunned by his adult children

Shunned by his adult children

I've been dating this wonderful man for about 1 1/2 years.  He's not from my city originally, so his adult children (both aged over 26)  live about a days drive away.  Earlier this year he asked me to travel with him on vacation to his home area.  We were to do some site seeing and take his children out to dinner (his daughters birthday was that week also) When we arrived his daughter informed him that she didn't want me at her birthday dinner.  I stepped back & said to take her out, I'd stay at the hotel, which I did.  I tried to talk with him afterwards about him needing to discuss "us" with his children to get their feelings, but also to let them know that we are in a serious relationship.  He doesn't seem to think there's a problem, but I'm concerned. Any advise or insite on adult children  who have a problem with a divorced parent who moves on with thier lives?