Without question, their favorite surprises are when I bake cookies after I've tucked them in and leave a couple on a napkin with a simple love note beside their beds. When they wake up in the morning, they find the treat and are always excited. My kids were VERY lucky this week and actually had cookie surprises twice.
I also really like to leave them little cards with pictures of us together, and for my older ones who are starting to read, I like to leave a simple letter telling them something they have done that I was proud of them for, or telling them what I admire about them. It is special, and it lets them know that I am noticing when they do good things. It feels good, for both of us.