Help with rhetoric

[Nunya Business]

I'm a new nurse and I used to be a CNA.  I'm having some trouble when I delegate to certain CNAs on my unit (It's a common tale, I know.).  Mostly my nursing judgement comes into question:  The CNA thinking the client doesn't need the precautions I'm implementing and becoming angry when those precautions are implemented after (the CNA's) disagreement is voiced.  I've involved management in the past, but it doesn't permanently resolve the situation.  
 

Note:  I lean towards safety when making decisions on care.  I recognize someone more seasoned may choose differently, but I'm still new and want to protect the patient and my license.

I am bringing this up for advice on rhetoric to use with CNA's in this situation that will carry an undertow of respect while explaining the necessity for the chosen implementation.  I don't want them to feel like their input isn't valued (although this is indeed how they are making me feel).

[Hannahbanana, BSN, MSN]

Rhetoric isn’t quite the word you mean, but I think you want words to use to get them to take delegation of actions that are legally yours to delegate. “Because I’m the nurse and I said so” might be perfectly true, but will not get you what you seek. 
Suggest  you find some time to peruse your policy and procedure book to start. If there is a policy that says XYZ will happen in the given situation as assessed by the RN in charge, and the actions to implement it are within the scope of the CNA job description, then next time this happens you can share your assessment findings and ask them to implement the appropriate XYZ.  
If they refuse, you say, calmly and with zero drama, “OK, I have made a nursing assessment indicating  the need for XYZ by our policy because of (specifics), and you are declining to accept the delegation per your job description?”

If they have an attack of common sense, accept the delegation, and do it properly, then thank them matter-of-factly and go about your shift. If they decline, then calmly say, “Thank you, I will write this up for your personnel file and pass it along to (whoever it is up the chain of command).” 
I can pretty much guarantee you that if you and the other RNs get together ahead of time and agree on the need for this tactic and apply it across the board for insubordination, things in the building will change pretty soon. 

Good luck!