Re: breastmilk sippy cup?
Yes, by all means put the pumped milk in the sippy! Pumped milk is only good for 6 months in a regular freezer (12 months in a stand-alone deep freeze), so unless you pumped that milk really recently you're unlikely to be able to use it to wean at 12 months- which you may discover you're not interested in doing, anyway! Make sure you do a taste test before offering the milk- stored milk sometimes develops a yucky flavor which could explain why your LO won't take a bottle.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"