Normally, one bag is enough for one tourist. If you go with your family, you can bring few bags. Why is a bag good for you? A small or medium-sized bag sits easily on the bus, train, car, taxi, and airplane. You don’t have to worry about it. When you arrive at your destination, you can jump to the ground easily. So, pack your things as light as possible, figure out the specific items you’ll need for your trip and stick to that list.
Packing light doesn’t have to mean going without. Just bring what you need, not what you want. Mix and match everything, so you can coordinate more outfits with fewer clothes. For example, if you pack all neutral pants, you can use your patterned tops with any bottoms. Keep your clothes tightly packed and well organized. Jakarta and java are not very cold places, you do not need to bring big & bulky jacket. Layering clothes and have a light raincoat/umbrella for colder/rain weather is better. Bring clothes made of fabrics that show a minimum of wrinkles and can dry overnight.
If you need an additional bag to go around or picnik, look for a large-capacity tote bag that can be rolled up into a pocket-size pouch. Bring your documents, money, travel info, etc in your small different bag.
Remember the goal: go casual, simple, and very light.