During interviews I found parents were either all for or against leaving daycare property so this is important to keep in mind if you are changing how you do things (some parents may leave).
When I had 5 kids the parents were all very happy that I stayed onsite. They all noted this in interviews.
I now only have 2 kids and we drive to playgroup and other outings, the parent provided a car seat and I am overly car seat safety conscious.
I am about to start taking the bus to the library for story time now that the weather is nice. But, I only have 2 kids, and both are behaved enough for this type of outing. It is after he morning rush hour so the buses are more empty than full. I wouldn't do this with 5 young kids as it would be tricky to seat them all quickly on a moving bus (especially if the bus is full).