Our friends stayed at Saratoga Springs in one the Treehouses... with their Grandkids and they are the ages of your kids... the kids loved it, and so did they.... The used the BBQ grill several times, and enjoyed sitting outside her youngest grandson, did not want to come in off the porch, he just loved sitting outside... Their grandkids live in the NYC, in Manhattan, so this was a real treat for them... as well the floor plan gave them the space that they needed, and that the kids loved.... They did swim a couple of times, and the pools were "cool" or "on point" as the oldest grand-daughter stated.... as far as the buses to the parks... they were okay with it, they have visited before... they did use Uber a few times, at night after the park closed just due to the wait time to get on a bus... they loved being close to Disney Springs, and enjoyed walking around in the evenings a couple of times, they really liked the restaurants over there... as far as use of the kitchen, they used it in the morning for breakfast, and for night time snacks... the rest they did character meals, and quick serve...
They will be back after school get out next year, and they always plan where they are going to stay next, and they all picked the Treehouses for the next visit....
So as a local, and passholder.... here are a few thoughts...
The parks are crazy busy during June, and the heat and humidity are even crazier....which is something that you should really take into consideration when plan your days...
Is having a kitchen a must... such as food allergies or something along those lines?
So when you say using the kitchen for meal prep... are you planning to make all of your meals? the reason I ask, even if you are planning to take lunch in the parks, you really need to have a way to keep everything cold, not just cool but cold... even something like peanut butter and jelly, will get melted and sweaty with the heat...plus the amount of water, or sports drinks you will need to keep everyone hydrated... will need to be carry in which is heavy... so extra weight to carry around...
If this is your first visit, and leaving the parks, no matter where you are staying takes time away from the parks... especially for a first visit, you are going to want to see things like the fireworks, parades, meet and greets of the characters. If you are planning on going back to the resort which I recommend that you do with the heat and humidity... You can figure on about 30 to 60 minutes for travel time... so a least 2 hours of travel time you should plan for.
Have you look at getting a family suite, with the kitchenette, you could bring breakfast items along, and get stuff for sandwiches... the cost on this would most likely be alot less than a DVC rental... plus you could look at maybe getting the Quick serve dinning plan, or even the Regular dinning plan... this way everything will still be paid for upfront... and you don't have to worry about meals...
I have a cousin that came with her family... and they were going to cook meals her reason was to save money ... she said that she felt all she did was cook, and wash dishes at the vacation rental, plus clean up and wash clothes the whole time that they were there, plus she said that they threw away alot of food, because they ended up eating in the parks, and that some of the food the brought in, was wilted, or damp from the humidity.... which is what her DH said that they should have done in the first place... their second trip they stayed at AOA in a family suite, and it worked out much better for them with Quick serve dinning plan, the third trip they got 2 value rooms with Free dinning, and upgraded from the quick serve to regular dinning plan, so that they could do a few character meals... now when the visit they go for the 2 rooms at a value... and get the dinning plan... this works for their family...
I would check out all the options, look to see if there are any offers out there, that might work for you... and run the numbers, and re-run the numbers... plus make sure to included the cost of groceries...