How to use a Private Subscription

I have the need to have a couple of subscriptions that are not seen by the majority of users on the subscription page. One is a free subscription for all content and is for a special case. The other is just like one of the regular subscriptions but allows for one additional page to be seen which provides some administrative functions. I cant let all users see this option. I have made these subscriptions private. How can I display these subscription options to a few users? alternatively is there a way to assign a specific subscription to a user? And if this is a private subscription, will the user be able to renew it at the end of the subscription term?