The debate between front vs rear projection can be slightly biased (depending on the cost, installation, and room set-up). For image quality, it has been said, and from what I have seen, agreed upon that rear projection is optimal for viewing. It works better in ambient light and your colors should be brighter altogether. I have installed and used many rear projection set-ups and this has a few benefits, mainly regarding installation. It gives you more space to play with, and in some cases, better ventilation. This like will give slightly more data:
So that is my take on the projection methods. Just keep in mind, that if you want to do rear projection, you have to make sure that you can actually set it up. With a 4K projector, you might need a lot of space. Check the the throw ratio on the projector you want, do the math and ensure that this is workable for your set up. Make sure you plan out the entire system and do all calculations before purchasing.
But is it necessary to go with 4K? Your screen doesn't seem to be larger than 10' and I have set up a lot of 10' screen that looked great with 1080p projectors. Will you be showing 4K videos, or is your company just willing to put in that extra $15,000 for the best possible?