How can I increase the size of the container without affecting the flow?

I have this custom keyboard:

When a key is pressed, I want it to increase in size without affecting the position of other keys around it.

The structure of the keyboard is as follows:

keyboard_key.dart：

return GestureDetector(
  onTapDown: _handleOnTapDown,
  onTapUp: _handleOnTapUp,
  onTapCancel: _handleOnTapCancel,
  child: Container(
    height: keyHeight,
    width: keyWidth,
    margin: EdgeInsets.all(keySpacing),
    decoration: _boxDecoration(),
    child: Center(
      child: Text(
        letter,
        style: _textStyle(),
      ),
    ),
  ),
);

keyboard_row.dart：

return Container(
  child: Row(
    mainAxisAlignment: MainAxisAlignment.center,
    children: rowLetters.split('').map<Widget>((String ch) {
      return KeyboardKey(ch);
    }).toList(),
  ),
);

keyboard.dart：

return Container(
  padding: EdgeInsets.only(
    left: 1.0,
    right: 1.0,
    top: 8.0,
  ),
  child: Column(
    children: _rows.map<Widget>((row) => KeyboardRow(row)).toList(),
  ),
);