@kaythaney Sorry for the delay on this. I've updated donatewiki with the changes requested: https://donate.wikimedia.org/?utm_medium=endowment. Let me know if this looks okay.
Like paymentswiki you now just need to include utm_medium=endowment in the link to get the new page, so the existing links on wikimediaendowment.org will go to it automatically. You might still want to update them to remove the extra parameters and fix the utm_campaign and utm_source values to something more trackable e.g. https://donate.wikimedia.org/?country=US&uselang=en&utm_medium=endowment&utm_campaign=endowmentSite&utm_source=endowmentSite
Also can we accept donations to the endowment from outside the US? If so we could remove the country=US from the link to allow donations in local currency.
Ok, I've added an appeal with the requested text to payments wiki. Set the appeal to 'EndowmentQuote' to get it. Like so: