First off I wouldn't announce that you are changing their diet. I would think that gluten free is more important than perfect paleo, so substituting rice pasta for wheat pasta is a good option. There are lots of good recipes and premixed gluten free flours available so you could make some baked goods in advance and freeze them. My son had blueberry GF muffins this morning and they didn't seem any different form muffins made with wheat. I used a standard recipe and just substituted GF flour mix.
I like to give protein, fruit and veggies first and then if more is wanted then consider the options I mentioned above. Since the kids have different preferences you could just set out a platter of assorted items and let them choose what they want. Some of the things adults avoid like potatoes, fruit, extra fat or nuts are actually better for kids.
Life is death. We all take turns. It's sacred to eat during our turn and be eaten when our turn is over. RichMahogany.