How to write an NFC tag with Driving Directions?
There is a way to create a link to a Google maps' destination which automatically detects user's location and triggers the driving directions. You can find how to do it here, in particular see the voice 'Directions (detect user's current location as starting point)'. You just have to write this link on your tag NFC, with any app that provides the possibility (like NFC Tools). The problem may be the storage capacity of your tags: this kind of link is bound to require a lot of bytes. You can choose the bigger size of tags, which cost more, but be sure the link fits, or you can use a provider of shorten link (which I suggest).

Edit: I didn't see you already tried something similar. With mobile browsers, like chrome, if you open a link that points to google maps you should be redirected to the app. Maybe you set your browser to open this kind of links by default instead of the app?