Google Analytics PII
Donate2 removes all parameters appended to a URL before passing the URL to Google Analytics
PII = Personally Identifiable Information
For good reason, Google Analytics does not allow any PII data to be included in their tracking.
Google's document on best practices for PII can be found here.
Here is an example of a secure Donate2 URL that contains parameters. The email address is considered PII. In this case, the use of the first name and last name can be considered PII as well. You could use the same URL shown below but leave off the email address and last name. You could personalize the Donate2 form with the persons first name and a specific ask amount. You could still display the number of years they have been a member and their current membership level.
Here is what it looks like in Google Analytics.