Well we haven't actually gotten the devices yet. Currently we use a D-Link DWR-921 for our guest wifi, but those things are pretty unstable. And you can only manage them if you connect a machine to it and not all our locations have laptops for example.
So the idea was to replace the D-Link for a Meraki MX67C and use the internal 4G modem for the primary WAN connection and use our MPLS network for management in case the 4G connection drops out for example or we just wanna change configurations regarding the 4G connection. For example we changed the option for roaming on a few D-Links but i had to go on-site to change it. Seeing we have over 30 locations in the Netherlands i am looking for a centralized system to manage it all.
We are currently also looking at Cradlepoint seeing they seem to offer us what we are looking for. Sort of hoping Meraki does allow this in the future seeing my personal preference would still be to use Meraki.
So in short: No Meraki devices in use yet, currently using consumer grade equipment and looking for a cloud management enterprise solution that will use 4G as primary and allow management through a MPLS connection.