A Maltese is a good choice for a family that has cats and is sometimes not at home. However, since your kids are so young, I cannot recommend a Maltese. I waited until my son was as old as your oldest before bringing a Maltese puppy home, and he still fell over on top of him when they were playing and injured the puppy's leg the first day.
If I were in your situation, I would wait until your youngest turns five. Your older child should be a lot more help at that time too.
A Golden Retriever is a good choice if you want a larger dog, as he is not as likely to become injured playing with the kids. He is more likely to become bored when left alone, though.