My understanding is that the upgrade to NW6.5sp7 will NOT upgrade edir to 8.8.x only patch it to the latest , is this correct ?

If this is the case, I would like to slowly move my servers which are currently NW65sp5 and edir to sp7, but not edir 8.8, is this ok or do 8.8 and sp7 need to be installed together ?

Last, I assume there are no problems mixing edir and because it is going to be a slow upgrade process with scheduling down time etc.