500m PtP connection is a piece of cake, all TP-Link outdoor access points can meet your requirement, you can refer to: http://www.tp-link.com/en/products/biz-list-37.html
So which one is appropriate depends on your other requirements, such as the speed, 2.4G or 5G, etc.
For now, CPE510 and CPE210 are the latest outdoor access points with relative better performance.

I have been looking at the CPE510 unit, I would assume I configure the one unit as a AP and the other as a client point them towards each other and it should just work. How important would line of sight be in this case? The distance is not very far, however i do not think we will have direct line of sight. there are some trees that might be in the way.

I think clear line of sight is important, sometimes it's even not enough, you can refer to: www.tp-link.com/en/faq-907.html
Anyway, what will the result be still need a filed test, if it's not feasible, why not just deploy them higher to avoid the barriers?

Clear Line of Sight and Freznel Zone isn’t everything; It’s the only thing.
Adapted quote from Vince Lombardi

Line of sight and clearance of Fresnel zone can save a lot of works.

Sometimes users are just wasting their time struggling with the damned obstacles/trees/walls in the way.

Once they ensure line of sight and clearance of Fresnel zone, everything goes on smoothly and the world gets better..;)