I hate to sound crass but those funerals will be a media circus whether the parents are there or not, I really don't think it'll make that much of a difference - it'll just be one more mawkish show of "grief" by a huge number of people who didn't know or have any connection to the deceased - it started with Diana and has continued with processions for fallen servicemen and women - I think it's distasteful.
Also, for a murder charge to stick the Crown will have to prove that there was "intent to kill". I think they'll have a hard time proving the requisite mens rea, with the obvious fall back to manslaughter becoming available. It is my guess, as a lawyer, that the CPS will have charged them both with murder with the hope that one will squeal on the other - they will have the lesser charge ready to go at the same time.