Hi Jessica! Your children are the perfect ages for you to visit Walt Disney World Resort and save; you do not have to take them out of school to travel. September is a designated Value Season time and you will save the most money by traveling then. In addition, you can either stay a few extra days because of the savings or upgrade to the next level of Resort hotel accommodations depending on your budget. For our first family vacation we were fortunate to stay at Disney's Coronado Springs Resort (a moderate resort) for the price of a Value Resort stay. We were limited by available vacation days and time off work, so it was nice to upgrade and stay within budget.
I would recommend that you visit
www.disneyworld.com and price your Vacation Package for Accommodations and Park Tickets with and without the different Dining Plans. For our family, the dining plan is worth every penny. My husband and I plus our 2 daughters eat the majority of our food, so the Dining Plan does save us money. However, my son does not always finish all his food on the Children's menu. He is often so excited that we have to make him eat and, of course, he would prefer to snack all day. I say this because with children your children's ages, you might be more likely to share your food or bring food for choosy eaters.
Keep in mind that more days that you stay and play, the more money you save. I love the no expiration option, especially for families with Toddlers and Preschoolers. If you would like to spend more time enjoying your Resort hotel, then you do not feel pressured to go the Parks because of your tickets. Save them for your next visit.