Taking trip with toddler and baby

My son is 4 months and my daughter is about to turn 3. For her bday next month we decided to go to an indoor water park resort for a couple nights.

It’s only 3.5 hours from us but that’s still long to be in the car especially for a toddler. (She refuses to fall asleep in the car)

Anyone have advice on what to bring to make the car easier? And also any tips on the resort/hotel to make us all sleeping in one room easier? My 4 mo old is sleeping through the night but I’m worried since he’ll be in a pack n play that it’ll be rough lol. (We just got through his 4 month sleep regression thank god)

Just looking for anything to make this more enjoyable for all involved 😂

I also don’t want my 3 year old to get too tuckered out all day and be over tired but want her to have as much fun as possible.

Any advice or tips is appreciated!