I think you are on the right path for documenting your trip and sharing your location, using social media apps such as Facebook or even Instagram along with their ability to constantly share your location with select friends and family. You will even be able to document photos along the way with these apps. You could also elable location sharing with your Andoid or iPhone device.
In case of emergency, we recommend a Spot gen 4, you can choose between an annual subscription or just for the month or months you are on your trip. You can get the device for around $150.00 then you have a few options for the plans which are roughly $15.00 a month. Using the Spot web portal, your family can check on your location whether or not you are within range of a cell tower. Additionally, the Spot gen 4 has an emergency SOS button to call for help if needed.