Picky Eater Help

I have a 3-year old DD who is super picky.  The child would eat a peanut butter sandwich for every.freaking.meal if I let her.  For breakfast, she will usually eat cereal or a muffin.  Lunch is always her beloved peanut butter sandwich with maybe some crackers and grapes.  I try to get her to eat whatever we have for dinner, but when she refuses, I give in and make her a sandwich.  She is on the skinny side so I want her to eat, but I always feel guilty about giving in. 

I also have a 2-year old DS.  He likes pizza, hamburgers, hot dogs, and chicken nuggets so it's easier to feed him a variety of things.  However, he is still not great with using utensils, so soup, chili, casserole type items are not all that practical.  I guess I can just let him make a mess while trying to figure it out??

To add to this, DH and I try to eat low carb/primal/paleo.  I don't think a lot of our meals are all that kid-friendly.  I guess I am just at a loss for dinner ideas that the entire family will eat.  The kids typically eat dinner at an earlier time since I don't get home until 6:00pm.  I really want to start sitting around the table as a family and eating the same meal, I just don't know how to get there.

Any tips/suggestions?  Please tell me I am not the only one struggling with this...