Your first time, two kids ages 3 and 5......MK no doubt!! Those ages are magical in MK!! You will have a full day's worth of things to do and see at MK, so get there at opening. You will want to make a dining reservation, most likely, so you will want to do a little research on where you'd like to eat for a special, memorable meal. There are some character meals at MK, but there is also Chef Mickeys character meal at the CR, which is a 10 minute walk from MK (or else monorail). If you have any questions, feel free to ask.