Since Singapore is relatively small (18mi x 22mi), I wouldn't suggest hotel hopping. Stay around the CDB (Central Business District), Orchard Road area. All the shoppng and major hotels are there. Swissotel - the Stamford is good (right next to Raffles). There is an MRT Station right there so you can go anywhere from that location. Since you are leaving early, I wouldn't bother moving to another hotel the night before you leave. Have the hotel concierge arrange for a van for the six of you. Singapore has a great zoo, Sentosa is a fun spot (small island acroos a causeway), Boat Quay (across from Clark Quay) has great bars and restaurants along the river. Chimes (near the Swissotel) has good restaurants and bars.

FYI - heading over there myself week of May 11th...