I would think 'inviting everyone' is far from inclusive. Just being told we are having drinks from 12, (with stories from previous year suggest clothes may be removed and behaviour may return to that of drunken 15 year olds) would be enough for most people I work with to turn down the invitation and to be feeling left out. If whole team did not feel sufficiently comfortable to attend, we wouldn't do it. Large quantities of alcohol is a definite no, no for some cultures or individuals. It is not a personal decision if what is happening is not acceptable to your religious or cultural beliefs (protected characteristic in law) so we would never support such activity during work time.
In our organisation it would remain gross misconduct to get your bottom out at work. It is indecent exposure and could offend many. I don't see anyone at work laughing about it. I asked my husband who runs an office based company and they too would sack someone for doing so. In a school you would be likely to face more than the sack if you did so. Ofsted would expect LADO to be informed and, if unlucky, could find yourself on sexual offenders register. It's just tacky, yobbishness and more than slightly 'rough hen party behaviour' that is not appropriate in many workplaces.
How it can be acceptable to behave in a way that is likely to cause offence, to exclude certain people and potentially breach the law yet cause anger to offer to get someone who is heavily pregnant a taxi, I will never be able to understand. This is not 'feminism' or independent women. Feminism is about women supporting and respecting each other - rowdy drunkenness excludes many and denying the additional support needs of pregnancy does women no favours. Women (actually, no, people) should look after each other not rip them apart because in a strange city, late at night they felt a little vulnerable.
Most of our staff are home based so an hour or two commute is the exception, not the norm. Three people stayed to go on to a wine bar. None went clubbing. Trains were dodgy but I don't think that was the reason.