Users having fine motor difficulties may drag their finger across the screen and then select a button based on the last icon touched before lifting their finger from the screen, or the first icon touched before dragging it further. While there is no setting within the app for detecting and deciding which touch to consider, you can use the iPad setting to achieve this. Here are the iOS settings that can help for this:

The settings used:
1. Select Settings > Accessibility > Touch > Touch Accommodations > Use Initial/Final Touch location


2. Turn on Touch accommodations = ON 

3. Enable it by triple clicking the Home button to enable touch accommodations. 

4. Whenever an icon / key is tapped there is a circle that is now visible to indicate the current selection - see circle in under the finger in the screenshot below. 

Click here to know more about how to use the settings: Touch Accommodations - read the sections on Tap assistance.