IME - The moderates are all centrally located enough that the difference in travel time to the MK will be minimal. The moderates all have more than one bus stop (well, POFQ has only one, but sometimes they share with POR) so build in a little extra time to travel around the resort before heading out.
Here are the distances between the resorts and MK according to the DIS:
CORONADO SPRINGS:
Magic Kingdom: 4 miles
PORT ORLEANS RIVERSIDE:
Magic Kingdom: 5 miles
PORT ORLEANS FRENCH QUARTER:
Magic Kingdom: 5 miles
CARIBBEAN BEACH:
Magic Kingdom: 6 miles
Honestly, I don't think your kids are old enough to care about the differences in the resorts, so I would probably pick whatever theme you and your DH like the best and go with that.
There are different things my family likes about each of the mods, so it's often just personal preference. For our tastes, we rank the resorts: CSR, POR, CBR, POFQ. But, I wouldn't hesitate to recommend any of them.
If you book CBR or POR, I would highly recommend booking a preferred room for location. CSR is a little trickier as preferred is close to the food court/ main building but standard is closer to the main pool. We book standard; business class is great if you can get it. POFQ is smaller, so the room category doesn't really matter.