V.N.
I am from Plainfield too. I think it took about 3 to 3 1/2 hours to get there. You will have a great time. I have been there three times with my now 22 month old son and he has always had a blast (as his 4 year old cousins).
We always stayed in the glacier canyon as it had a kitchen and living room. (two bedroom suite- the one we stayed had one bedroom master and the other bunks) I like that we could eat breakfast and lunch in our room and went out for dinner. Lunch at the resort for your size family could easily be 40.00, eating in your room would be more cost effective if that is a concern. You could always order in and that would be less expensive then eating on the resort. We loved Moose lodge for their pizza. I would avoid Pizza pub.
There is an outdoor waterpark that is fun right outside glacier canyon, but the other ones you do have to walk about a block (covered indoor bridge or outdoor walkway)or more. My favorite waterpark was the inside wave pool with kids activity center closest to glacier canyon, but I did like the outdoor one near glacier too. We went mid week and the inside ones were much less crowded. If you can request you may not want to be on level 2 of the hotel as that is the main walkway and it is not an issue so much in glacier canyon but the other areas of the resort it can be loud at night.
Have a great time! any other questions feel free to message me.