Ah that's what is using so much memory, I thought you had just a basic 3D scene.
I had the same issue when I jumped from Gingerbread to Honeycomb, the RAM usage was almost double and could not figure out why. I'm assuming it's the result of Android taking advantage of the larger RAM sizes in newer devices to minimize GC pauses.
There is a simple solution but you will need to have separate APK's for 2.x and ICS.
Honeycomb introduced the large heap parameter in the AndroidManifest.xml file which increases the application RAM from the usual 16GB/24GB/32GB size to 256MB.
Add android:largeHeap="true" to this tag:
<application android:icon="@drawable/icon" android:largeHeap="true" android:label="@string/app_name" android:debuggable="false">
Also ensure the minimum SDK is set to 11 if you want Honeycomb support, or 14 for just ICS support.