Invoke --data-checksums using pg_createcluster on Ubuntu 14.04
After further investigation, to specify the default initdb arguments used in pg_createcluster, the below was added in /etc/postgresql-common/createcluster.conf:

initdb_options = '--data-checksums'


Then pg_createcluster was run as normal and show data_checksums displays:

data_checksums 
----------------
on
(1 row)