I asked one of my teachers regarding this when we came across a hadith in Sahih al-Bukhari that had this usage. He basically said what you seem to be hinting at. Although there is nothing inherently wrong with using عليه السلام for ahl al-bayt (may Allah be pleased with them) and some of the `ulama of the salaf did use that for ahl al-bayt, since it has become a salient feature of the Shiites in our time, it is perhaps best to avoid it. Also, it has being the norm that عليه السلام is used for anbiya', رضي الله عنه is used for sahabah, and رحمه الله is used for anyone after the sahabah, so it is best to stick to this convention as not to confuse people. Other `ulama may hold a different position on the matter; either way, it isn't a big deal.