I managed to do it in the shutdown script by changing the script to
umount /dev/mmcblk0p2
/resize2fs /dev/mmcblk0p2 <size>
umount -afr
...
and copying resize2fs into the root directory, the beauty is that once executed the scripts are wiped clean across the reboot because / is in ram.
After the reboot I reduced the partition size to match in fdisk.