your plan looks almost the same as what i did going from the 175g to the 270g. how i do it (4 moves and counting
) take the first couple pails of water before messing with any rock and set those aside to put the fish and corals in in the pails that have fish i add an air stone ( makes a huge difference in how well the fish do over the course of the move and the days that follow) next i keep pumping out water as rock is exposed i put them in bins filled with tank water keeping them submerged as much as possible so as to minimize any die off. as the rock comes out take advantage of any easy catches.once all rock is removed catch any remaning fish and do a head count to make sure every one is accounted for. once the water is at the same or close to the level of the sand i dig a bit of a hole in the sand and move the pump there and move the discharge to waste as its typical full of crud you don't really want to transfer across to the new tank. remove the sand if in doing this you notice a rotten egg smell i would use all new sand if not you can use the existing sand. then out with the old and in with the new
plumb as nessasary add sand then rock refilling as you go. once filled check parameters and acclimate fish and crack a cold one