Not attending this event but this thread offers women’s experiences of using women’s toilets and why that single sex space is so necessary and valuable to women and their kids.
www.mumsnet.com/Talk/womens_rights/3203454-What-do-you-use-the-womens-toilets-for
Also, all single sex toilets are already gender neutral. You can express your gender however you like in a single sex toilet. It is not required that men should be allowed in to use the women’s toilets. Such men should either campaign for a third space for themselves or use the men’s toilets.