We took our daughters, then ages 1 1/2 and just turned 4, last September. We just went to Oahu as we didn't want to island hop with them. We spent 7 days at the Marriott Ko Olina Beach Club Resort. It was the best vacation we have ever taken!! (shh, don't tell Disney

) Our girls just had the most amazing time! I never wanted to leave. We had been twice before we had kids, once for our 15 day honeymoon (did all 4 major islands) and for our year anniversary (just did the Big Island), but this was amazing to go with them. We didn't plan much. Just played on the beach right outside the hotel,n swam in the pools, swam in the lagoons there, did some touring, like North Beach, and just relaxed. Our hotel was condo-like, so we had two bedrooms and a living area with a full kitchen. We ate most breakfasts in the room, had snacks, and ate two dinners in as well.
The only big thing we did was a pirate ship cruise. It was fun, but very hot. My poor toddler was not thrilled, although my 4 year old enjoyed it, mostly. Next time, I won't plan anything and we'll go with the flow. We did that most days, and those were the best ones. I'll never forget my 4 year old taking a hula lesson under the palm trees or my DD1 relaxing for 45 minutes and being practically asleep on my lap while we sat in the lagoon and the water just covered our legs. Both of them were very sad to leave, and DD4 talks about it a lot still.
We did do the character breakast at the Disney hotel right down the road from us (we had decided against staying there because we could get a suite for the price of just a small room at Aulani, but we were right in the same area.) I actually was glad we didn't stay there. It was very hectic compared to our resort, and the pool area was so crowded. The breakfast was the busiest and most hectic character meal I have ever been to. I wouldn't plan to do it again. I do love Disney, but it did not feel relaxing to me at all.
We used frequent flyer miles for our airfare, but I know it is very pricey. I will say it was just the best time, so I think it would be well worth the money. We were planning to go back next year, but decided to go to Guatemala with a family friend, so probably the year after that. I know we will be back though!