Your family will need bigger space than an individual or couple on little house design. If you work from home you will need more space. The whole idea of living simply in small spaces is that the true value of the home is realized, and the home doesn’t become a burden. In other words it’s about finding balance and the first step is reducing the number of possessions.
Most people park their mobile tiny homes on their own property or at friend or relative’s place. Some folks travel and move around from place to place. Jonathan built a Tumbleweed Fencl and is moving from campground to campground. Sam built a tiny adobe in New Mexico and kept it tiny to avoid building codes.