How to be sure that your adult children want to be around you? Okay, first of all, your children are grown, and it's time to let them go. How do you do this? They have been your responsibility and your life for many years, and now you are expected to just let them go out into the world on their own; free to make their own mistakes, without your help and guidance. Impossible?
If you are going to be able to have a good relationship with your adult children, you are going to have to learn to treat them as adults. They are no longer your little babies, in the sense that you need to tell them what to do.
But what exactly does it mean to treat them as adults? It means that you only give your advice if asked for, you bite your tongue the rest of the time. They truly must be free to make their own mistakes, just as you did. It means that while they are always, always welcome to visit, they are to live on their own and take responsibility for their own lives. It means that when you visit them, you never ever criticize where or how they live, or who they live with.
It means that you call them before you are planning to visit, you do not just drop in. In other words, you treat them as you would any of your adult friends. This is not being formal with them; this is showing respect for them, for their lifestyle, for their choices. This is, of course, if they are not drug dealers or on the run from the law or some such. I am speaking of the ordinary person trying to make their way in this world.
The quickest way to alienate your adult children is to criticize their significant other. Bite your tongue until it bleeds, if you must. This is the one they have chosen, and whether you like it or not, if you want to continue to have a good relationship with your adult child, you must be as friendly and cordial to their mate as you would be to any other person you would meet socially.
Keep being their friend and keep being there for them for whatever they need, and help them in anyway that you can, but back off about butting into their lives. Your reward will be that they will want to be around you more, and that is after all, what you want, what we all want.
Invite them over for dinner, don't just let them assume that they are welcome any time. Although of course they are. Don't try to buy them with gifts. Allow them to make their own way, just as you did. If they need to borrow money, make up a contract, just as you would with anyone else. No one should expect anything less.