After visiting the Tiber island why not continue across the Ponte Cestio bridge and walk onto Trastavere. This is a popular area among locals and tourists with authentic restaurants, pubs, cafes and a busy everyday life.
If you would like to visit even more church in Rome (after visiting the St. Peters Basilica, Santa Maria Maggiore and the Lateran Basilica) there are some quite nice churches at Trastavere as well. On a warm day these churches can be nice to visit just to get away from the sun some minutes.
Enjoy Trastavere and know that you can easily spend quite some hours just walking around enjoying the atmosphere of the area.