No, not too many kids! There are actually a moderate number, because once you're there it is a very child-friendly place; but I've never felt overrun.

We've always hired a car, so I can't speak of the bus service from first-hand experience. It seems to be pretty reasonable from Kirkwall (and to a lesser extent from Stromness), but poor from anywhere else (unless, of course, you want to go to Kirkwall or Stromness).

The twice we took taxis, they were easy to get hold of and had low fares per mile, but distances are fairly high so the fares do add up.

Your best bet might be to stop in Kirkwall and take busses where possible.