Is there a reason you aren't staying on site the first part of your trip so that you can't switch it to on site then off? Maybe it could be worked that way?![]()
Because you have to buy the tickets with your room in the form of a package in order to get the DDP. That means the tickets have to take effect the first day you stay onsite, and not before, unless you split the amount of days on the tickets. But that results in your paying more for the tickets.
Do you realize you need only one adult AP to book the AP package? If you can buy an AP for one of the adults, then the onsite stay can be accomplished with DDP without buying more tickets for everybody else (assuming there is availability for AP room/dining packages for the time you are traveling. I would check availability before I bought an AP if you are going to use the AP just to get DDP.)
If you have already purchased the tickets for everyone, I don't know if this will work. You can upgrade one adult ticket to an AP while you are still staying offsite; if you do that before you check in at a Disney resort, and you have one adult AP in hand at checkin, then you should be OK.

I'm not that familiar with how the packages work for AP holders. My understanding of the DDP is that everyone in the room has to be on the same package in order to get the DDP. You could book for example eight nights and get the dining plan for eight nights but you don't need to purchase 8 day tickets.
What about buying park passes separately for nine days (I think the price would be around 20.00 less per ticket), then book your resort, purchase a one day park ticket for each person in your party and book the DDP that way? The one day passes cost around 70.00 each for adult tickets. From the ages of your kids it looks like it would cost around 250.00 more to do this but you'd be able to get the dining plan during your on-site stay for everyone in your party. Just a thought
I hope everything works out for you and you have a great trip.
On site guests are always going to have additional perks. And as an on site guest your extra perks will begin, once you check in for your on site stay.The DDP is part of a WDTC package. Tickets, meals, etc, on the package will not start until you check in on the package.
If someone in your party is an AP-er and 21+ years of age you could instead purchase the DDE membership that allows 20% off on sit down meals, and some counter service meals. And adult beverages are included in that discount.
That might work better for you anyway as that will cover your WDW dining for your entire stay -- onsite and off.
I don´t have a problem with the perks beginning once I check in, that´s a given in my opinion. But I still don´t get why I shouldn´t be able to get that perk once I check in, just because I also chose to spend some days at the parks (and spend my money there) before I check in.
You can, you just have to purchase all the elements of the package which includes tickets.
The dining plan is part of a package because Disney is trying to capture all of your vacation dollars not just some of them. They don't offer it guests who are spending part of their vacation off-site because they don't want you to stay off-site.
It really boils down to one thing - the DDP is only available as a package add-on. A package is defined as room AND tickets. Even those staying onsite for their entire trip are not eligible for the DDP if they book a room only reservation. The two exceptions to the room/tickets package requirement are:
1. DVC Members staying on points may purchase the DDP for their party
2. AP Holders are allowed to book room a room and DDP with no ticket requirement.
Remember though, that with both of these options, your reservation becomes a package and is, therefore, subject to the change and cancellation stipulations for packages.
If you really want the DDP for the onsite portion of your visit, your best alternative is to get an AP for one adult in the party and book your onsite stay as an AP/DDP package. Having an AP will also get you some additonal perks like 10% off at the World of Disney Store in DtD, reduced admission to the water parks, etc.
So to book a room with an AP rate, only one adult need have the AP to get everyone in the room the DDP, Do I understand that correctly?
Is there any way I can check online whether there is AP availability for the dates I need?