Could Tiger Cubs reach Heligoland Bight?

Would the first Tiger Cubs be available for the Battle of Heligoland Bight in August 1914?

No: their likely commissioning window is September to November 1914, after the battle.

The timing rules the Tiger Cubs out of the Battle of Heligoland Bight. Even an accelerated first batch is only expected to commission between September and November 1914, whereas the battle was fought in August. Royal Navy acceptance trials also make a much earlier operational date unlikely. Their first credible wartime effects therefore begin with autumn deployments such as reinforcing Cradock, not with the opening North Sea actions.