No problem. It IS already allowed for all users. All programs are allowed for all users, unless they need administrative capabilities and the user doesn't have it.
All you've got to do: tell them to make a shortcut to the program. Even easier: put a shortcut in the Public desktop folder and/or in the C:\ProgramData\Microsoft\Windows\Start Menu\Programs folder. Then all users will see it. That's the only difference between 'install for all users' or 'install for current user only': the location of the shortcuts. Those are easy to add (or move) later.
Kees