Yes, you will have room for a crib in your Category 4 Family Suite. It may be tight to maneuver around the crib (which is actually a pack n play) to get to the murphy bed or verandah but it will work. We had essentially the same setup on our cruise last year and did fine.
If you are set on having a verandah, the cat 4 is a great way to go. If you would consider going without a verandah, you would most likely save money and get more room by booking connecting (not adjoining but connecting) cat 10 (inside rooms without a verandah)rooms. You can leave the door open between the rooms and you get two bathrooms, two closets, two tvs etc. Just something to consider. You do have to pay for 2 adults in each room and 1 child in one room but generally it is still cheaper than a cat 4 room. You could also look at porthole rooms for a little more money if you'd at least like a window.
An upgrade to a cat 3 one-bedroom suite would be very nice although not really necessary. The suites (cat 1-3) are all quite popular and book quickly though so you would have to check on availability. The cost, in general, to upgrade from a cat 4 to a cat 3 is several thousand dollars for a 7 day cruise.
I would suggest getting a quote on
DCL's website (
www.disneycruise.com) for the cruises you are considering. This way you can play around with combinations of rooms to see what will work best for you. You can compare the prices for the different category rooms and for different weeks etc. Be sure to make note of the inclusion of insurance and transfers if that is important to you. You cannot check prices for cat 1-3 online but can check them by phone as you explore your options.
Happy cruising and Welcome to the DIS boards!!!!!