Last summer, we purchased 3 day Dollywood/water park tickets for $89 per person. You could visit either park on the same day, or in any combination that you wanted. It was an option on the Dollywodd website last year.
We only stayed 3 nights last year, and just visiting Dollywood/water park, it took up most of our time. We did play mini-golf a couple of times and visited the outlets.
We stayed at the Christmas hotel and it was a real treat - I would highly recommend a stay there.
Could this have been a length of stay pass purchased in a package with your hotel? If so, this wouldn't be available to OP since she is staying in a timeshare.
We've had Dollywood season passes off and on for about 16 years. Last year was the first time we've had Super passes for both parks and it was our first time visiting Splash Country. So, I'll try to impart all of my so-called wisdom to you in one post!!!!
It looks like the Great American Summer program is going on again this summer with fireworks and extended hours (it used to be Kids Fest in the summer). Don't miss the bubble show if they have it again this year. Even my dad liked it! A season super pass is pretty much your only option if you plan to visit both parks on multiple days. They have pre-season pricing and payment plans on their website now. One of the members of your party could get a gold super pass. It gives you free parking and 20% off of merchandise and food. If your kids want to play a game, you can get a free game with purchase of a book of Dolly dollars if you ask the person running the game.
We usually buy 1 refillable mug and take others from years past. We buy the 99 cent drinks in the refillable mug and then pour them into the other mugs for the kids. At Splash Country, we could use our Dollywood mug to get 99cent refills but Splash Country sells a more expensive refillable mug that gives FREE refills and you MAY be able to use that at Dollywood to get free refills there, too. I also suggest a refillable popcorn container if your kids like popcorn. It's worth it after just one refill.
A great place for the fireworks is up at the playground with a rubber mulch floor in Timber Canyon. Your kids can run around or whatever and you could sit on a bench and enjoy the fireworks. We've done this a few times and only a few other people were there. Last year, DD was thrilled to fulfill her goal of riding the Wild Eagle during the fireworks.
It sounds like you'll have a stroller but in case you need a locker at Dollywood, there are some at the river raft ride and some in Timber Canyon (some other places, too). They cost 50 cents and you get a key. If you want to go back and switch things out, you'll have to pay another 50 cents to lock it back and get your key again. You can't take stuff on rides here like you can in WDW- even the flying elephants! Also, parts of the park are steep and there is one hill that is sort of textured and hard to push a stroller on.
It used to be that Dollywood pretty much cleared out before closing and you could ride something like the raft ride over and over again. With the extended (til 10pm) Summer hours that has changed. The lines can get really long at Dollywood but the Q2Q would be pretty expensive for a party your size.
I had never been to to a full fledged water park and we really enjoyed Splash Country. If you want to ride River Rush (the water coaster), I would suggest that you get in line first thing. Get in line before it gets hot!!!!! We were in line for almost 3 hours in the afternoon!!!! But the kids begged and we gave in. It was fun but not worth 3 hours wait. Don' think you can go just before closing and get in line. They didn't cut the line off but if we were still in line at closing, they told us the park would close and we wouldn't be able to ride.
There are sort of play areas for different aged kids. It appeared that some people set up a base camp at those areas- or the wave pool- and some stayed there all day. With young kids that might be your best bet- stake out a spot near the area you think you'll be most of the day. There is a little playground for really small kids and a shallow swimming area for bigger kids in another part of the park where people seemed to stay alot- plus a larger kids area that is like a McDonald's playland with water. It was hard to keep up with where the kids were at that playground and I just had to plant myself near the entrance while we let them play there.
Renting their cabanas is really expensive. We usually put a towel or two on a couple of chairs near the lazy river in a plastic bag (in case of rain) and stowed the rest of our stuff (refillable mugs, etc) in a locker. You get a discount with a gold pass on the locker rental.
We left our vehicle and rode a tram to Dollywood to see the fireworks in the evening. When we left, the tram driver would not take us to our vehicle- even though where we parked said "Tram Stop H." He offered to take us back to the park where we might be able to take another tram but we didn't want to wait anymore. Those crowds are awful at closing. We walked (mostly in the dark) and had to stop crazy-park-leaving traffic to cross the road. So, just drive over to Dollywood if you choose to do this!!!!
Close your mouth if you ride the train, you could get ashes or soot or whatever in your mouth! You will get soaked on the River Battle and some grown men had no mercy on me or my DS who was 4 and just soaked us thoroughly. I had so much water in my face and he was so slippery I couldn't stop him from climbing over the top to his Dad on the other side of the ride!!!!
Your kids will want to get wet at the "farm" area near the barnstormer. Take extra clothes. I've seen little girls in bikinis but I think it's against the dress code. DD wore her bathing suit with a skirt and a tshirt over it. She took off her tshirt before she got in the water. DS usually wears swimming trunks and a tshirt. DH & I also wear quick dry clothes.
I don't have a food suggestion other than check Groupon to see if they have any deals. Have a great time!
But it sure sounds fun! 
And there are a couple bars we want to go to. Hogg's Upstairs Taverne in Gatlinburg is one. It used to be Hogg's and Honey's. And we want to try Dick's Last Resort, I'm looking forward to the "sarcastic" waiters, as I used to wait tables and would have loved being sarcastic to some customers! 
