The Starwood Amex is the one I would go with. There is no limit to the number of points you can earn and the points can be redeemed for hotel stays or transferred to most major airlines for flights. It would be easy to track how many points you guys have and split them up 3 ways. As far as only having a $100,000 limit, that shouldn't be too big of a problem. You can make payments mid cycle if needed.