A group wants to maximise the potential for surprise attacks using their stealthy members. They don't want their less stealthy members to blow a surprise attack.

A party of four; two stealthy, two not. The two stealthy members travel in to a room (~30 feet or so) and leave the two non-stealthy members behind the door/in the previous room (hidden).

The two stealthy members throw for surprise attack on some monsters in the room. After any surprise attack round, combat starts proper and the two non-stealthy adventurers enter the room and enter combat.

Is this valid?