Creating fields isn't data entry. I smell an improperly structured database. Post the name of the fields currently in your table and what this new field(s) would be called.
Giving users access to the table isn't a good idea, you should look to use a Form, therefore they are limited to seeing what you have created on the form.
It isn't a good idea to allow them to change the structure of a database as it has many different implications down the line.
The database is for the owners of a business, and they want to be able to navigate their database easily with buttons, but also to be able to view already input data.
Data that has been input can easily be viewed with the use of Queries or within forms themselves. Queries can be designed so that they operate off of forms with flexibilty for the users. Here is an example of how that might work.