Need help with SVG text animation

My code below shows two circles, numbered 1 and 2, floating around on
paths, with their radii varying in size.   I want the tags, '1' and
'2'  to change size pro****tionately, but I cannot figure out how to do
that.

Can someone help ?


<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg
     xmlns="http://www.w3.org/2000/svg"
version="1.1">
<path id="path1" d="M100,250 C 100,50 400,50 400,250"
        fill="none" stroke="none" stroke-width="0"  />
<path id="path2" d="M150,350 C 110,100 350,150 450,550"
        fill="none" stroke="none" stroke-width="0"  />

  <circle cx="600" cy="50"
        fill="red" stroke="blue" stroke-width="10"  >

<animate attributeName="r" dur="5s" repeatCount="indefinite"
 from="10" to="85"/>
<animateMotion dur="6s" repeatCount="indefinite"  >
       <mpath xlink:href="#path1"/>
</animateMotion>

</circle>

<text id="TextElement" x="590" y="55"
          font-family="Verdana" font-size="35.27" visibility="hidden"
>
      1
    <set attributeName="visibility" attributeType="CSS" to="visible"
           begin="0s" dur="6s" fill="freeze" />
    <animateMotion dur="6s" repeatCount="indefinite"  >
       <mpath xlink:href="#path1"/>
    </animateMotion>

</text>

<circle cx="100" cy="200"
        fill="blue" stroke="yellow" stroke-width="10"  >

<animate attributeName="r" dur="5s" repeatCount="indefinite"
 from="10" to="85"/>
<animateMotion dur="6s" repeatCount="indefinite"  >
       <mpath xlink:href="#path2"/>
</animateMotion>
</circle>

<text id="TextElement" x="90" y="205"
          font-family="Verdana" font-size="35.27" visibility="hidden"
>
      2
      <set attributeName="visibility" attributeType="CSS" to="visible"
           begin="0s" dur="6s" fill="freeze" />
      <animateMotion dur="6s" repeatCount="indefinite"  >
       <mpath xlink:href="#path2"/>
      <animateTransform attributeName="transform" attributeType="XML"
           type="font-size" from="1" to="3"
           begin="0s" dur="6s" fill="freeze" />
    </animateMotion>

    </text>

</svg>