I'm not a parent, but I'm still young enough to remember being a child, and I'm also of the appropriate age to observe young children and how they are treated by their parents.
You're being a great mother, I know you are, but I'm with robdar on the "teaching children the meaning of the word no" concept. If you don't teach your children that they can't always get their own way, then it's not gonna be pretty when they get older.
I have a 11-year-old cousin who is very spoiled, as is her 14-year-old brother. Their parents have a lot of money and so they always get what they want. I babysat for these kids in the past, and I also spend a lot of time with them when I'm at home (I'm in university), so I know full-well what happens when a child never hears the word "no". If I tell the 11-year-old that she can't have something, like candy at 9am, she will yell, she will disobey me and try to get it herself, she will threaten to tell her parents, she will lie to me and if all else fails, she will cry like a baby. Why?? Because she's so used to getting what she wants that she can't handle it when someone says no. And if she does something wrong and warrants a scolding, she cries like a baby and screams that her parents hate her. This when she always gets what she wants. Sure, she's still young, but she behaves like a spoiled baby when she's almost in junior high. She treats other girls her age like garbage, she tells them that she's better than they are, she teases people who don't have as much money as she does, she's quite intolerable.
I know you're having a great time being a mother and I know you're concerned about your children and their upbringing, just be sure not to spoil them too much and teach them the difference between right and wrong and teach them to appreciate what they have and to understand the meaning of "no". That's the best advice I can give you, and believe me, they'll thank you for it when they're older. My parents taught me to value the things I have and not to expect to always get what I want, and they taught me the meaning of the word "no", and I think I'm a better person for it today.