I love blues and siamese. My best breeding pair are siamese.
Keeping the wheel in the cage won't hurt. Your rats will probably appreciate it. Mine are in theirs constantly. Just make sure it's the right size for them.
Picking up a single level maternity cage is a good idea. Wouldn't want babies falling off the levels. haha
Chocolate is an agouti hooded dumbo. Vanilla may be champagne/fawn variegated dumbo. (variegated is like hooded, but instead of a linear marking along the spine, will have patches)