This app was mentioned in 10 comments, with an average of 1.40 upvotes
I don't think any of these will go above 150
Pairing a launcher with lockable home screen along with Giganticon is how I usually handle it for my senior clients.
Well, for big icons, you could use https://play.google.com/store/apps/details?id=com.gabetaubman.giganticon&hl=en for android.
Don't think there is something like that for apple.
Apple is going to come out with new tablets on March 27th, so, I suppose I would wait to see what those offer.
What I do is with a android tablet, install Droid VNC Server (there are other ones as well, I just happen to use this, since it has source code I can tweak), then if something happens, I can remote into it, and fix whatever needs to be fixed, or show them how to do something. Save a 5 hour trip each way doing it remotely. :)
Probably used this
https://play.google.com/store/apps/details?id=com.gabetaubman.giganticon
Giganticon lets you change the size of icons on the homepage. It treats them as a widget.
Nova launcher or for better icon size customization on home screen use Giganticon
https://play.google.com/store/apps/details?id=com.gabetaubman.giganticon
What about this app ? If i am not wrong it will work with every launcher. giganticon
If you need truly large icons, this will help. https://play.google.com/store/apps/details?id=com.gabetaubman.giganticon