Im sorry, but just based on your reply, you have never used family echo on mobile or you see no issue in the site being basically unusable on mobile.
A mobile app would greatly help the site in multiple ways and spread the word of it. However, Just making the site itself Mobile friendly would lead to more people using the site in general.
Needing to Zoom in and out just to use the site is not mobile friendly (three different mobile devices have been used to test the site, all have the same result)
If you zoom to far and no longer have access to any buttons or menus, you are forced to reload the whole page. This is extremely annoying and not mobile friendly.
The text size can not be changed via browser and you must change your entire devices text size. This is already very big issue in itself.
In short, in not making the site mobile friendly. They are simply driving people away as only people with a Desktop or Laptop can effectively use Familyecho as intended.