Best Theme Bedding for my kidos...

Why not ask your kids what they like? Otherwise you'll be buying them Tranformers when all they really want is MLP.

For the bedding, I would stick with basic bright colors that they may like and would go with a lot of things - then you add a theme to it with maybe decorative pillows, stick on wall clingys, posters, and so forth. Problem with the kiddies is their likes and dislikes change quickly. That way you can keep the bedding for several years and change out the other stuff so they always have their room decorated with stuff they like.