I've tried to find a direct link to a check-in box in facebook.
This is the code that I found, on https://touch.facebook.com/Scoutsgroep.VZW.De.zwaluw/, I have tried to put the code on a website (wordpress) but that doesn't create a direct link to check*in on the page.
<a class="_55i1 _58a0 touchable" data-store="{"action":"\/page\/checkin\/?id=315057520648","inputname":"status","targetid":1093893470,"pagename":"Scoutsgroep VZW de zwaluw","pageid":315057520648,"placeholder":"What are you doing?","composertitle":"Check In","pinplace":true,"forceasync":true,"log_data":{"under_more_button":true,"page_id":315057520648,"source":null,"referrer":null,"platform":"mtouch"},"event_name":"tapped_check_in","module_name":"pages_public_view","nativeClick":true}" href="#" role="button" data-sigil="touchable touchable page_checkin m-pages-log-event"><span class="_55sr">Check In</span></a>
Later on I would like to use the created link to make a qr-code that automaticaly checks-in to the facebook page
As far as I know, there's no direct link for a check in. Facebook doesn't want people accidentally / maliciously being checked in to a place.
I suggest that you use the URL you have, put it into a QR code and let the user decide whether they want to check in.