I think doing this is going to be vital. If you don’t want male voices to dominate, you will need to keep that element out of the process.
When dealing with a group that isn’t used to having their voices valued, you may encounter hesitancy to speak up. Just because you label the space as “safe” and they hear that, it doesn’t mean that they are going to behave as if it is safe. You’re dealing with an entrenched narrative that says speaking up can be bad. I suspect you will need to undermine that narrative from the very beginning. Fwiw, this is what I would do.
In the first question, I would ask them to tell a story about the most positive interaction they have had with another individual or group online. As they share their positive experiences with others online with your online group, I would hope that they would connect the experiences in such a way that they would feel good about what they are doing and more connected (and identify) with each other (yay for oxytocin). Those positive feelings should strengthen the willingness to trust one another as you begin to ask more and more self-revealing questions, as I move from self-affirming stories (easy to tell) to other-criticizing stories (harder to tell).
And don’t forget to weave what you are doing in the fabric of a narrative that is much bigger than just being part of a focus group. Tell them of how you hope what they are doing will open doors to greater understanding and action that will be felt by others across E. Africa. This visionary story will help to weaken the grip of the one that stifles them.