Unless it’s an old behemoth, take the MBP. Not only will everything be easier and, perhaps more familiar, you will also have access to full LR. Lr Mobile is great, but it lacks gradient masks and adjustment brushes and spot/healing/cloning.
Consider also... Can you be sure of upload speeds to CC when you need them? What size of storage is on the iPad (I assume, perhaps incorrectly, less than the MBP)? Besides weight and size, what’s the advantage of the iPad?