It never feels like enough, and you worry that there might be a distance growing between you.
In that case, all you can do is be yourself and be loving with your children.
Fighting fire with fire and saying bad things about your ex and her new partner is very counter-productive.
Truth be told, this way is better than the alternative - I'm sure you would NOT prefer that they fought about everything.
It can be hard enough to maintain a good relationship with your children if there's just a limited amount of time you can spend with them.
Don't shy away from asking about things they do with him – although, in most cases, children tend to be garrulous, so they'll probably tell you anyway. Your kids don't need to know that there's a turmoil inside your head and heart.