It is invariably the case that HM or another top Royal will present the VC, GC and GM - in fact I cannot think of an occasion when they didn't. During WWII, King george VI travelled in Royal aircraft to bases to present these medals [like to Guy Gibson, ISTR].
I consider that it is perfectly acceptable for the head of the Armed Forces to present other awards as HM's representative. Don't forget, HM is getting on in years...