I am helping a friend convert his 1980 built pool that has lots of issues into a play pool.  It has a large deep end and no diving or sliding equipment.  We gather it would be best to fill the deep end with crushed road base and then some soil then do a 9x9 grid of rebar. We will be bringing the drains up obviously and probably centering them more in the pool.  Then we will either have concrete poured at 6 inches or have gunite installed at 10 to 12 inches thick.  Should we chip the walls on the sides to ensure concrete/gunite adhesion or drill and tap rebar in?  Also 1/2 or 3/8 rebar?.. Should we completely demo the bottom out of the deep end to make sure there are no voids under the plaster as there are cracks in the current shell.  Should we drill 1 inch holes in the deep end if we don't demo?  I am thinking it needs to have at least a 6 inch depth difference from the shallow end for better circulation and for the drains. If we do bust out the deep end it would be a cleaner plumb job.  Just a thought. But I do not want to cause another major settle.  Thanks. Any advice would be greatly appreciated.