Children often come back with very creative answers of their own. Encourage them in their thinking and imagining process. Who knows, their answer may be closer to the truth than one you could ever conceive. Create a designated worship space in your home. Use various places to worship.
Variety keeps it fun.
Start a ritual or a pattern that as your children grow older they can carry on as a concrete memory of spending time with God when they were young. How about Friday night worship by firelight or candle light or maybe even with incense. Do not moralize or preach. Talk and pray about challenges and everyday choices to be made in school or at work. Imagine a sailing ship made of wood.