Ask HN: Engineering Retreat Ideas

In 6 months, we will have an engineering retreat (flying remote folks in, hotel rooms, etc) where we'll meet at our home office (between Ventura, CA and Santa Barbra, CA). It will be about 30 folks, most of which have never met before. With a budget of about $65 p/p p/day does anyone have any recommendations for activities?

Building something that each person can take back home would be a plus; the cost of Raspberry Pi's has us considering alternatives...

I'm open to anything!