Ferry from HK to Macau and back

We only have limited time to visit Macau (from HK), and we plan to go to Senado Square and Ruins of St. Paul, then to the Venetian Hotel before going back to HK. Is it ok to buy one way ferry tickets for each trip since we don't know what time we'll be able to get back? Can we go to Macau via the Macau Ferry Terminal, then take the ferry from the Taipa Ferry Terminal to go back to HK? Thanks.