Have you considered using a purpose built GIS app for this? I also manage a team of staff collecting soil samples where there is little or no internet connectivity. The staff use a combination of tools on iPad and iPhone to get the job done. On their iPads they utilise a FileMaker solution to collect geo-coordinates representing a sampling transect - no internet connectivity required, just need to be able to acquire a GPS signal. On their iPhone they use a tool called CartoMobile. It can be preloaded with shapefiles (points, lines, polygons) and imagery so the staff know where they are going. It is also possible to modify the shapefiles using forms to capture new data, or geo-coordinates if you wish. All of the necessary data for CartoMobile can be prepared in advance using open source GIS solutions such as QGIS assuming you have access to some imagery. The dbf part of the shape file (essentially the table) can then be manipulated using FileMaker back in the office to integrate the field data into your solution, or alternatively CartoMobile can integrate with spatial data infrastructure to get that done.