Hi, Diana!
My opinion is that if we're going to be dining in the park anyway, then the Dining Plan is the best way to go.
The reason I love the Dining Plan is that it allows each of us to order our favorite entrees, even if they are the most expensive items on the menu, without worrying over how much this will add up to (especially now that my ten-year old foodie is an "adult" on the plan. He can order the filet mignon without having to check with me about price.) With a few character meals scheduled, the Dining Plan will really pay off for you, too.
The way we work around the plethora of desserts is that we always opt for whatever is lightest as well as what is portable. I'll bring an extra baggie to house those Quick-Service desserts (i.e. cookies, muffins or capped, individual-sized cakes) so that we'll have them either later in the day or at night back at the room, rather than see them go to waste.
At our Table-Service meal, the kids usually have plenty of room for dessert, but my husband and I do not. There, we'll either see if there's something that we can order to go (again, saving it for later) or if there is a milkshake or smoothie option which can be put into to-go cups as well. These often come in handy later, too.
While I know that we've not been able to substitute sides for our dessert, you may be able to ask your servers if there is a fruit option for dessert that you could then get to go as well.
I suggest that you check out
the menus for Quick Service options, in case you'd like to choose where you'll dine partially based on your dessert options.
Please send more questions as you think of them! I'd love to help!