The safest way is to try and use Access 2007 to develop and modify your database until every users upgrades to 2016. Otherwise, you could try to avoid using any "new" features to try to keep the database compatible with 2007.
You could try the following steps:
- Get a working copy of the 2007 database
- Keep a backup copy of it
- Try to modify the Access 2007 database using 2016 by only adding one feature at a time
- Test the new database in 2007
- If it's not broken, try adding the next feature you need using 2016
- Test it again
- Keep doing this until you figure out which feature of 2016 is not compatible with 2007 and then figure out another way of doing it
Hope that helps...