You can mix, but often this will result with two pulls but YMMV
I did a 3bm for myself and bunch of family members in aug 2011 and only got 1 pull. i applied for amex prg, business gold, and delta gold. got instant approval in all cases. not sure about chase though, they seem stricter.
also with chase i did an app for my wife and was denied. when i called recon 2 weeks later, they approved the card, but they did another CR pull, just fyi...