Some things to consider on your hotel:
* the Hyatt is not within walking distance of DLR, so that means you will either have to drive or take the shuttle. Daily parking at the theme park means a $15/ day fee. I think there is also a mandatory parking fee at the hotel, but I haven't stayed there in almost 10 years. Also, I'm pretty sure the shuttle only runs once per hour.
* I LOVE LOVE LOVE the Disneyland Hotel, but it is EXPENSIVE. There is nothing quite like it at Disney World, it is truly a special place. There will be discounts released about six weeks before your travel dates, which historically have been anywhere from 20%-30% off.
As far a weather in January goes it is incredibly unpredictable. It could be sunny and 75, or it could rain for 5 days straight. Bring layers though, days almost always start off cool, then warm up (if its not raining), then temperatures drop again once the sun goes down.
In terms of park strategies, they really are similar to Disney World: get to the park for rope drop and make good use of Fastpass. Unlike WDW however, Disneyland still honors Fastpasses past their expiration time.
If you have any more questions as your planning shapes up please let me know!