L.A.
If you read the paper, magazines or books and see articles, cartoons or quotes, cut them out (or make a copy from the book) and leave it for that child. Tell them it reminds you of them..
I love the idea of rotating who has the honor of running errands with you.
I am sure you already do this, but every once in a while tell each child what you admire about them as an individual and what they bring to the family.
My mom (I felt) had to really give a lot of attention to my sister. She was spirited (polite way to say high maintenance) child that really needed lots of attention.. Every once in a while I would need some reassurance I was still noticed. My mom would tell me she was seeing all of the things I was doing to stay out of all of the drama (sister) and to keep from taking away from that and she appreciated that I was so independent. She would also point out my accomplishments, which I was not always sure she knew about. It only took a few moments, while we cooked, or carried the groceries in, folded cloths, whatever. made a huge impact on my self confidence and let me know that when you love someone, there are times we are really busy, but we are still aware of the other person at all times..
This has helped me in our marriage when I realized we had not had an actual conversation with my spouse in days or weeks.while our child was young..