The spelling of Sholom was a reflection of the Ashkenazi heritage of these founders and pioneers. Most often, when you see the Hebrew word for "peace" it is spelled Shalom. This is the transliteration of the Sephardic pronounciation. Even though most American Jews are of Ashkenazi background, the Sephardic pronounciations are more popular because Sephardic Hebrew is spoken in the State of Israel.
Beth Sholom means "House of Peace." Actually, the word for "House of" would be more like Bet in modern Hebrew, or Bes in Ashkenazi Hebrew. In Sephardic Hebrew, the actually phoneme at the end of the word is a soft T, sometimes rendered T H to express the slight aspiration which softens the T sound. Thus, it became common to transliterate the word for House as Beth. In time, English speakers began to pronounce the word like the more familiar female name.
Thus, our Congregation's name means House of Peace, even if it is a combination of a misinterpreted transliteration of a Sephardic word, and the Ashkenazi pronounciation of another.