You should not include UTM codes for outbound links. Stephen already pointed out the main issue in that you don't know how they tag their campaigns and therefore without working directly with them it's impossible to provide them good tags (even if you can guess how they're doing it now they may change it).

Also you don't have to include UTM codes for them to know the referral is coming from you. That will already be in the Source information in Google Analytics for any clicks that came from your site. Stephen mentioned this but the traffic wouldn't show up as Organic traffic. Instead it would just be normal Referral traffic and could be found under the All Referrals section under Acquisition. 

If you'd like to know on your side how many people are actually clicking on these links you could use GA Event Tracking to track the click events on these links. For information on how to do this check out this Google Support answer. https://support.google.com/analytics/answer/1136920?hl=en

So basically don't do this. You should only include UTM codes for links to a website if that website has both asked you to do so and told you what codes they want you to use.