Hi, yes it's safe. 4am the trek starts, guide will give introduction for sometime and the trek begins. It's easy without guide as well as all head to same route. Ensure you reach by 5.45am to view the sunrise, different colors of sky.
Yes, it is safe to go early morning and best for you to have the experience of Sun Rise :) As you have booked from an agency, there will a guide provided to you.. Provided take a confirmation from them before you start off your trek.