Here are my suggestions:
1) In the meeting itself (and I do realize in your specific case, it's too late for this, but just for future reference) whenever there is a refusal of a parent request (or anything else you think should be documented in a PWN), make sure to state very clearly, "Can you include that refusal (or whatever) in the PWN?" Sometimes they're caught off guard and say "yes." Either way, you have them "on record" as either agreeing to include it or not. If they agree and it's not in the PWN you receive, follow up with an email reminding them that they agree to put it in the PWN. [Sidenote: Since it sounds like you're having problems with documentation following a meeting, you might want to consider recording future meetings. Then regardless of the language in the PWN, refusals, etc., are documented. I don't know what state you are in for purposes of telling you whether you have a right to record (you have the right if it's a one-party state), but even if you are in a one-party state, school districts can limit that right in a school board policy, such as requiring 24 hours' advance notice, so make sure you comply with any school policy on this issue.]
2) Although LEA's do have some discretion, they still have to follow the law regarding PWN's. So use the language from the IDEA regarding PWN's, as well as any pertinent state regs or laws. Also check your state Department of Education website, specifically special education compliance department (or just call), to see if they have put out any policies or guidelines regarding PWN's. My state DOE has a very detailed list of what is required to be on a PWN. If any of the IDEA language/state laws or state policies are on point with what you are asking for in the PWN, quote that language in your request for a correction.
3) If it is a PWN that requires parent signature (unfortunately, most don't), write a note below your signature that you disagree that XYY was not set forth on the PWN. That way, XYZ effectively IS on the PWN.
4) ALWAYS follow up with an email after you receive a PWN that you disagree with detailing specifically what you feel is missing or incorrect (including the REASONS BEHIND the decisions - a very common requirement that is often lacking in PWN's, in my opinion) . That's still documentation and the next best thing to having it in a PWN - and will hopefully be enough if your matter ever goes to due process, especially if the LEA wasn't following requirements set forth in the law regarding PWN's.