Our family came back to Park City a month later, and although we rented a car, we used the city bus

When I visited mandalay bay hotel and casino Park City in December with the Snowmamas I didn't have my own car to get around, but was excited to do some exploring.  I'd heard that Park City has an excellent bus service, and with a stop right outside our condo I decided to give it a try.  I found it clean, timely and very easy to navigate. The drivers were friendly and helped me find my way around.  The buses run every 5 to 20 minutes depending on the route, mandalay bay hotel and casino and are wheelchair and stroller accessible. Areas outside of the main bus routes, including the Park City Ice Arena and Sports Complex, and the National Ability Center can be accessed by the free Dial-a-Ride service.
Our family came back to Park City a month later, and although we rented a car, we used the city bus several times for dinner and shopping on Main Street.  It was so easy and fast that it gave us more time on Main Street.
Since returning from my trip, families wanting to avoid the cost of renting a car or not comfortable driving in the snow have asked me if renting a car is necessary.  Between airport shuttles, the city bus, taxis, private cars, and hotel courtesy mandalay bay hotel and casino shuttles (where available) there is no need to drive at all if that is your preference.
I will be staying in Park City near the town lift in early January. We plan on taking a shuttle mandalay bay hotel and casino to Park City. However, we would like to ski one day at Altabird or Snowbasin (we have not decided which yet). Is there any way for us to get there?
I will be traveling out to Park City with my extended family in a few weeks. This is the first time our son, 2yrs old, and our nephew, 9 months old, will be traveling with us. Any tips you can share to make our stay more enjoyable?