We go that time of year -- for the last three years -- and I would go with a moderate. My son really liked the POFQ at those ages. The slide was perfect for him and he could do it by himself at age 5. That made him feel great. The resort is smaller and easy to navigate. Not a long walk from any of the rooms to bus, food court, lobby, store. And, we like the theme with the cobblestone walkways and the alligators and music at the pool. Rooms were just redone and they have a refrigerator in them, now. The playground area is perfect for your three year old and POR has a more challenging one for the 5 yr old.
The nice thing is if you want, you can walk down to POR and go "fishing" using a Huck Finn type of set up. You pay for the worms and pole. It isn't very expensive ... and you can swim at their pool. Most times it is warm enough to swim -- depending on what you are used to ...
The deluxes are nice, especially at that age, if you stay at a MK resort --probably Polynesian would be my choice. But, for the price, I think you would have a great experience at the POFQ. Didn't care for CSR or Carribean Beach. But the POR and POFQ are nice. That is probably just personal preference as many like those moderates. At that age, though, I wouldn't stretch my budget. Go with what you are comfortable paying for ... that will make your trip a little less stressful.