Hi @geraikenangan,

In practice any 8-port gigabit switch would be fine.  In practice the switch goes inbetween your ISP router and the AP's  That is to say, the switch acts "like a splitter."  The OC-200 can be connected to either the 8-port switch or the router -- it doesn't really matter -- but I would tend to put it on the 8-port switch.

But there are a few factors to consider:

1) Whether or not you want to / can power the AP's using POE -- more expensive switches can supply PoE power to some devices (depending on the voltage, specs, and power budget)
 

2) Whether or not you want to separate the management of the OC-200 onto a private VLAN -- this helps keep people from "hacking" into the OC-200 and the AP management pages.  But it much more sophisticated to install.  Probbaly out of scope for you at this time.
 

3) Ethernet cabling distances & material (be sure to use Cat 5e or higher (preferrably Cat6).  Shielded cable is recommended with shielded terminations.  Remember the 100m is the maximum end to end length from switch to AP.  But best practice is to limit this to no more then ~90m or so.

4) Weather proofing and grounding -- the switch and its power supply needs to be protected from the weather and the chassis grounded to serve as a ground for the shielded ethernet cables. 

I'd still recommend the EAP225-Outdoor over the 110's.  I realize they cost more (twice as much $70 vs. $35/each) but for your extra money you get two radios (2.4 and 5.8) and 802.11ac (aka Wifi5) both of which will help you significantly given the number of clients you're expecting.

-Jonathan