I want to be the one to create accounts for my members

Hi Everyone,

My site is for a nonprofit startup. Donors are considered members. Their membership dues are collected on Flipcause. I want the ability to create a Shopify account for them after they become a member. This will automatically apply a discount on our merchandise and give them access to every page on our site. What I dont want is the ability for just anyone to sign up for an account. Does this make sense? How can this be accomplished?

My website is www.PennsylvaniaParks.org

I want my merch available to everyone but discounts to be available to donors only.

I will also have a page that is only available to members, not everyone.

Thanks for your suggestions in advance.

I hope this makes sense.