2. Custer State Park
This one takes a little prepping for but you will have an amazing time! Pack a picnic and bring more food and water than you think you will need, especially if you are traveling with little ones. I always made sure to bring the DVD player just in case the kids got fussy. There are a few visitor centers with restrooms but it could take you awhile to reach one. If you do stop at the visitor center, ask the Rangers where the buffalo are roaming that day. Yes, where the buffalo roam! They will tell you where the heard was last spotted and you can pick up information on the different types of animals you may see in the Park.
We always had good luck on the Wildlife Loop which is a 15 mile drive and will take about an hour. There are some beautiful overlooks where you could stop and have lunch and let the kids stretch their legs. You may see buffalo, mountain goats, deer, elk, and moose to name a few. There is a herd of wild donkeys on the route that hangs out along the road so bring some apples and carrots. They are hand fed by park visitors and will stick their heads in your car window if its down. This drive was always a family favorite.