If this is your first trip, to WDW or
DCL then you have come to the right place...
Both options have pro's and con's...for a first trip or any trip really... You will need to match apples to apples to see where you think the value lies for your family.
For cruising you will need passports for all of you so that is an added cost that should be worked to the DCL budget if you don't already have them.
Entertainment - At WDW you get all the entertainment, rides, fireworks, meet and greets and parades for on ticket price. On cruises there is entertainment, there are character meet and greets....
but when docked you will want to do excursions, while the ship is big its not that big, and if your going to cruise the point is to get to see little bit of other countries, and check them out, snorkeling, swimming with the dolphins, kayaking, beach days, shopping, horse back riding are all available. I could not imagine not getting off the ship.
Transportation -
you can use DME ( Disney magical express buses) to and from either WDW here in Orlando or DCL is docked at Port Canaveral.
Resorts are where you can really customize your vacation. - Value- Moderate- Deluxe - The values have smaller rooms but if your going to be in the parks all day and night, and just use them for sleeping and showering, you should be okay, the pools are nice but no slides at the values... Moderates there a more roomy feeling and the main pools have slides, as well there are what they call quite pools if you need relax from all the excitement for a while. Deluxe resorts are the largest rooms with the largest price tag, the pools have slides as well. I will say that all the pool are done really well and really wonderful theming. There are pools on the ship but at times you might find them closed. So if swimming when ever is important take that into consideration.
Dinning - on the cruise ship almost dinning is included ( there are a few adult only options)... remember that soft drink packages are extra, and not included with the price of the cruise. As well as adult beverages cost... I will say, DH and I think that they are around the price per drink on either vacation. AT - WDW you again can sorta customize your dinning plan, the plans are per person per nights stay... and can be spent in any order you wants and are good from check on arrival day to midnight on departure day..... QS - is 2 qs meals and 2 snacks,
DDP - is 1 QS meal and TS meal and 2 snacks, DDXDP is 3 meals for however you want to use your entitlements, with snack and I think a adult beverage included for 2018. Or pay OOP for your meals... But adding in Any dinning plan is in order to match apples to apples, for budget purpose's.
On the DCL - there is a whole floor for kids to enjoy but this does come with a added cost. WDW - they do offer babysitting for a grown ups date night.
My suggestion is... That for your trip - you stay at either a Value such as POP, or Moderate Caribbean Beach so you still get some of the island feel... Go with the DDP this way you get some options for character meals, and some mom and dad meals. Or go with QS and plan on at least one character meal out of pocket, especially if your daughter is into princess, and I would lean toward breakfast as its normally the less expensive option for this type of dinning. DME transportation to get you to and from the airport, is your not driving. As far as tickets you could do 1 park per day tickets, or you might want add in park hoppers for a weeks stay.... I would go this route.