A few thoughts frm someone who has gone to WDW many times with extended family:
First, it may not be fair to judge how kids react to non-WDW parks vs. WDW. I'm a good example. At non-WDW parks, especially if it is a pay-per-ride type situation (fairs?) I rarely ride more than one ride. WDW is almost the opposite- we ride almost everything at least once. There are also so many interesting things to see that are not rides- like real gardens, educational displays (Innoventions), interactive water fountains. The food alone is enough to send me running from most amusement parks. Think about/discuss what common interests you share.
If you are dealing with differing endurance levels, then I think offsite is the WRONG choice. I speak form experience. When we stay offsite, there is a TON more pressure to travel together. It is also MUCH harder to get everyone going in the morning. We also had considrabel disagreement about which gorceries to buy. Eveyone wanted somethign different, then we fought when someone took the wrong food! The $14 parking fee alone is reason to travel together. I have seriously found the complete opposite to be far more effective- stay at the best onsite hotel you can afford! If value is where youa re at, that's okay. skip the mods. If you can swing deluxe- do it! Also since you said offsight might be an option- strongly look at the Swan and Dolphin. They offer some pretty good deals, and when it comes to trnasportation- they are equal to a deluxe, for about the price of a mod. You just can't get ME or
DDP. Not only will it be much easier for everyone to deal with transportation, but it will also make you feel better about compromises. I have little desire to hang out at uninteresting hotels;they are just a bed. Disney resorts are FUN to explore. The pools, extra amenties, decor...all make hotel time enjoyable.
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Ah...I just read back thorugh the posts....if this is your frist trip to WDW, I'd reconsider your plan to go together - at least for this go round. Another option to consider- is to plan to meet up just one or two days- or have your trips overlap by just one or two days. That would reduce the pressure.
Another way approach is to merely splurge on a deluxe resort those one or two days you plan to spend together. A split stay will help you shift gears mentally.
money. Try to avoid committing your money on them. (including a cc hold on anything) If you are going to do prepaid dining, or places that require a cc hold, have them prepay you well in advance. Maybe consider the dining plan. The dining plan is a good way to estimate food costs. Look at what each meal plan offers, then add $ for tips. Don't expect the plan to save much money, but it serves as a good estimate of what food costs are. Also, it serves as a commitment.