Fun day out for employees...

100% agree

Hi Violetta, love the idea of setting up a committee to come up with suggestions as 400 people is a large amount to consider. Setup a charter for the committee (google it, there are lots of examples so that the committee have direction on what they need to consider). Also useful to have a budget for all or per division, that way you know what you're working with. At the CIPD festival of work we came across an organisation called Bowles https://bowles.rocks/ not sure where you are based but they also come to your office and are used to dealing with large groups as well as working on any strategic HR goals such as diversity & inclusion as suggested below. The committee can also help you to get volunteers to co-ordinate for each division/team where they need to be and what they need to do leading up to and on the day. Finally after lots of work and planning, have fun and enjoy the day with the teams!