NOR/SI Guide Principle 5 says

The NoR/SI should, when possible, use words or phrases from the racing rules.

We often say that using the language of the RRS helps rules discussions.

So yes, it's a good idea.

I wouldn't obsess about it.

I use 'changes' for the magic words 'This changes RRS xx'.

I use Amendment and Amend for changes to the NOR/SI but I wouldn't argue if someone preferred to say 'changes'.

I have no problem with 'up to' and often use it:  If we're talking about the number of races per day or session it may clearly say what I want to say.

If we're talking about Scoring RRS J1.3(5), I'm aware of some classes that like to maximise the number of rapid fire races in a regatta:  they could use this, but I prefer to set a hard number of races to score a series.

Amendment Vs Change 
Could you take a 10 year old and say "I am amending Rule 31 so that if you touch a mark you don't need to do a 360 degree penalty" and they would definitely know what amending means?
If you said changing could you? 
And what if English is not their first language? 

According to the (Google) dictionary... 

Not all dictionaries agree about the change being minor or to be fairer. But a change to the RRS in a SI or NoR does not have to be minor or fit that matter fairer. The words "this amends" and "this changes" while mostly seen as synonymous might actually be different...?

Similarly "up to" can be ambiguous. Is it up to and including? If the suggested alternative were "no more than" is any ambiguity removed. Again, imagine that the NoR was in French or German. While you might think you could translate, would you be sure if it was up to and including or not?

It is sometimes worth putting a phrase through a reading age tool. The younger the age, the more inclusive the text. 

A common SI phrase might be:

"Personal floatation devices must be worn at all times while afloat. This changes rule 40."
(The firstword.co.uk/readabilitytest: 66 with changes, 60 with amends). 100 is most readable.  

If we do the same with up to:
"There will be up to 7 races, with up to 4 races per day" then both score 100!

Calum, good get with the ambiguity of 'up to'.  So draft as:  'Not more than'.

Calum, I can’t resist pulling your leg about the reference to a “360 degree penalty” in your question:

“Could you take a 10 year old and say "I am amending Rule 31 so that if you touch a mark you don't need to do a 360 degree penalty" and they would definitely know what amending means?”

Whether or not 10 year olds would understand “amending”, they might well not understand a “360 degree penalty”, since it disappeared from the RRS 10 years before they were born! (end of December 2004).

I suppose it goes back to something that Dick Van Eck told me when I started on the international circuit: when writing decisions, use the words from the rule itself. Following on from that, I would use 'change' but would not be upset if someone else did not, as long as the meaning is clear.

Following up on Joseph's comment, when a rule is changed the NoR should say  "This changes RRS xx." "This amends RRS xx" would definitely be less desirable. But when the change to the NoR is posted, it's preferable, in my opinion, to call that change "Amendment n".   

Callum makes some good points, but to be really pedantic, rules should say "shall" rather than "must", because "must" has multiple meanings, as in "I must not know what I'm doing." Also, a rule in the NoR specifying when PFDs must be worn doesn't change rule 40.  Rule 40.1 specifies that PFDs must be worn, and Rule 40.2, titled When Rule 40.1 Applies, says "Rule 40.1 applies if ... (c) a rule in the class rules, notice of race or sailing instructions states that it applies." Finally, that rule should be in the NoR, not the SIs, because it might affect a competitor's behavior before they come to the event -- they might, for example, buy a more comfortable life jacket than the one they currently own.

Ang - as has been explained to me, "shall" is a command and "will" is a promise.  In the case of the RC, in the NoR and SI "promises" are being made to the competitors that the RC will do something and if they don't then redress is possible, see J1.3(7) for example.  There are also times where the OA or the RRS command the RC to do something, like publishing the SI.  You will notice that in RRS 89 & 90, it's all "shall".

The competitors are always told "shall" since the competitors can't make "promises" to do something.

Thank goodness this isn't a high-stakes contract, or we'd be in court forever.  But as Michael says, this distinction between "shall" and "will" isn't just from the RRS; it's standard contract language.  If you issue a contract to somebody to replace your roof, the contract you make with the roofer might say "The owner will give the roofer access to the property from [such date to such date], and the roofer shall complete a new roof on or before [such date]."  There are lots of rules in the RRS and in the NoR and SIs binding race organizers, and obviously many of them aren't enforceable because there's no penalty you can apply to those people for breaking rules.  As for redress, that depends.  To be successful, a boat requesting redress has to convince the PC that her score was made significantly worse by the failure of the race officials to follow their own rules.  In many cases that's not true (e.g., "There will be a mandatory competitors meeting at 0900 ..." and the meeting isn't held until 0930), but in other cases, it might be true ("The first mark will be a yellow inflatable buoy" and the RC uses an orange buoy, then the first boat rounds a nearby yellow buoy instead and fails to sail the course).

my simple view.  An amendment is the document that contains changes