Such a heartbreaking situation. You, like every other second wife, have a tough road because he has so much history with his first wife, plus they share having created kids together. And there is nothing stronger than a parent-child bond, too.
You literally have to "dangle" your own goods, services and benefits in front of him constantly. How does he feel when he is with you? Do things that make him feel 1. respected (a man needs respect from his woman), 2. young and free, 3. sexy and virile. He needs to feel that when he is with you, he is the man he wants to be.
He loves his daughter and grandkids, true, but he will not want to feel like the old, burdened man all the time.
I tell you, it all boils down to that because the human mind is hard-wired to move toward pleasure and away from pain. Be careful never to represent pain in his life. Only the pleasure.
Second marriages don't have any greater success rate than first marriages. Don't give him ultimatums or force him to choose. Just whisk him away often for weekends of amazing good times. When his conniving, mooching daughter wants to come around, he won't feel too bad saying, "I can't! I'm going out of town!" Be sure your sex life is fantastic because you are the only one who can provide that, and every man knows how critical that area of marriage is for a contented husband.
Stock your armory, girl. And he'll choose you every time. No need to feel betrayed. He isn't doing this consciously. It's a matter of bonding time. You don't have the edge when it comes to length of time spent with him so make every minute with him count. Pick the battles you can win, and remember that your goal--and remind him of this--is to make him, not you, happy. So when he wants his daughter to come over with the kids, leave out some treats for the kids, give him a kiss, and then slip out for some of your own fun. Tell him you want him to visit with his kids without any tension so you'll get out of the way, but you'll be back. With a special surprise for him. wink, wink. He will keep his visit with her very short.
Then go out and have a blast doing what you like to do. Come back feeling exhilarated, fulfilled, joyful. He will want to get in on that feeling instead of his daughter's snipping about you, the woman who represents joy in his life.
Just my thoughts.