You’ll want a stroller for your baby. The ones that hold the infant car seat are convenient, especially if they convert for the older child.
Babies can go outside as soon as the family wants to take them out. Keep baby shaded and dressed for the weather. It’s enclosed spaces and close contact with lots of (potentially sick) children and adults that newborns should avoid.
The stroller should be affordable, light, and easy to clean. It should fold up and fit in your car without much fuss. By the time your child is a toddler, you may want a very minimal stroller. For the zoo and amusement park, you will be leaving your stroller unattended—something to consider when pricing them.
Most children outgrow all but the most industrial strength strollers around four years of age, and by that time, they prefer to walk, especially if the activity is one they enjoy.