In Aruba, take the local bus from the bus terminal across the street from the pier. You can get off at any beach you like and reboard the bus when you're done. The round trip fare for 2 was $5 in 2009. What a bargain! You can either stop at Eagle Beach (no restroom facilities) or go up to the hotel area and gain access to the beach from there. All beaches in Aruba are public. Be sure to take a towel and some bottled water. The water is wonderful!
You girls will have a great time.