Hi Mike
I wouldn't recommend it.
Your building code may insist on a protective earth anyway, leading to insurance issues if you don't include it.
Even if this isn't the case in your area, you should still use an earth.
Theoretically you won't need it, as long as the genny head is completely isolated from ground, but this can never be guaranteed, no matter how careful you are.
You should also fit an earth leakage circuit breaker (RCBO) in the output to protect you from any faulty equipment you may unwittingly try to power from your new circuit.
These may not work, if a proper earth connection is not made!
Also, bear in mind, nothing can protect you from harm if you somehow manage to contact both live and neutral (or any two phases!) at the same time.
Electricity generated at home is just as dangerous as the stuff the power company supplies...
sparks