I think you need to consider what would happen in an emergency, especially during Bank Holidays holidays when a lot of senior staff are unavailable. Also, one cannot assume that hospital staff are dementia aware - disappointing but true.
For example what would happen if your loved one became seriously ill whilst in respite and you were abroad? Giving the care home a copy, means that the DNR issues are dealt with in your absence.
This may sound blunt, but these things do happen.
I wanted to make absolutely sure that Mum's wishes were recorded and they have been in her LPA for Health and Welfare. Our solicitor chose appropriate wording and our GP has a copy.
Mum has had a number of emergency "adventures" recently. I always mention the LPA when discussing her care and then, if necessary, say which investigations or treatments I consider appropriate, given that she has dementia. I've never had any problems to date.
If there are any issues then these can be communicated and discussed at the outset. Clear guidelines enable a good working relationship with hospital staff - at all levels.
Some solicitors charge a reduced fee if you take out both LPA's together.