Special events should be held at extra special places. If you have a company and you have an upcoming launch for a new product line or have updates for major changes that will be observed throughout the year, it should be properly announced to everyone involved within various departments. Since your conference rooms won't be enough for this kind of event or anything similar to this that would include a massive amount of people, there are other options that you can take. Perhaps alternative venues would be the best way to go around things.
Alternative venues are actually rental spaces that come in a wide variety when it comes to the design and accommodations that would match different types of events; from small to big ones. There is not really a need for you to make things complicated. If you think the function hall within the facility that you have just won't be enough, renting an alternative venue would be your best resort. This would also be ideal for personal occasions like wedding anniversaries, birthday parties and so much more.