You can update camera to the center of bounds of markers. For that -
Create LatLngBounds.Builder
object and add all the markers in it.
LatLngBounds.Builder builder = new LatLngBounds.Builder();
While adding marker store it to variable like
Marker marker1 = mMap.addMarker(....);
Marker marker2 = mMap.addMarker(....);
Then add all markers in it using
builder.include(marker1.getPosition());
builder.include(marker2.getPosition());
Then build LatLngBounds
LatLngBounds bounds = builder.build();
Then create CameraUpdate
and animate camera to relative position
int padding = 0; // offset from edges of the map in pixels
CameraUpdate camUpdate = CameraUpdateFactory.newLatLngBounds(bounds, padding);
mMap.animateCamera(camUpdate);
And done.
Refer this answer for more details.
Hope it'll work.