"These women would be happy if you were to call them."
Translation:Queste donne sarebbero felici se tu le chiamassi.
contenti would be incorrect because queste donne requires feminine inflection. contente should be OK. In this case it would be contente because gender and number matters with inflection of contento, but only number matters with felice, for which the plural of both genders is felici
Chiamassi is correct for both Io and Tu. In a conversation between two people one could say, “Queste Donne sarebbero felici se le chiamassi”, but it would be ambiguous because it could either mean, “if I were to call them” or “you were to call them”; the use of Tu or Io untangles who the caller would be.