I would suggest cheating.
The point of a model/dio is to represent the subject and aid in understanding. If you try to model the solar system to scale, you end up with a basket ball sized sun in Chicago and a marble sized earth in Sheboygan. Interesting, but not terribly useful or practical.
So what do we do? We cheat a bit on the distance scale.
Make them in the larger scale and place them at a closer distance. That way you can see the subject and model in a scale that has some detail.
Otherwise you have two specks and a vast ocean. Accurate, but not very fun!