No, morning dew will not be enough for grass seed. The level of moisture that new grass seed needs, or indeed, a full lawn, will not be able to be met by morning dew. Morning dew produces moisture, but not in enough volume to ensure the soil underneath your lawn gets a good soaking. As well as this, the sun will soon evaporate any moisture left by morning dew before the soil has had the chance to soak it up.
You need to ensure you water the soil regularly to ensure that your seeds germinate. It may be a good idea to water the ground whilst the morning dew is still down, and it is recommended that you water before 10 am, anyway, to give the water a good chance to soak in before the sun dries it out too much.
Remember, your seeds only get one chance at this. If they dry out too much then they will die and you will not get the lawn you desire. You will have to start the process again.