We've been 9 times since 2005. Usually squeeze in a DW trip a month or so after a major national park expedition. Split between Fort Wilderness or their many resorts.
Yes, Hot, Sticky, AND fun. I love it...kids and wife love it. Yes, it can be more exhausting than hiking in the mountains.
I'd forgo the dinghy unless you want to travel outside DW resort as a whole. There are so many transportation options in the park you don't need the dingy. You can save a bit of fuel not towing it, and one less thing that can go wrong.
Pull in the park, relax, enjoy, and have fun. DO IT...you won't regret it.