You can animate your camera within specific bounds. Let's say you have an ArrayList of markers, something like (this could also be a list of LatLngs, doubles, anything that contains the latitude/longitude for your marker)
List<MarkerOptions> markers = new ArrayList<MarkerOptions>();
You can then make sure they are all visible on your map by doing the following
LatLngBounds.Builder builder = new LatLngBounds.Builder();
LatLng position;
for(int i = 0; i < markers.size(); i++){
position = markers.get(i).getPosition();
builder.include(new LatLng(position.latitude, position.longitude));
}
LatLngBounds bounds = builder.build();
map.animateCamera(CameraUpdateFactory.newLatLngBounds(bounds, 15));