The Little Man learns different than the Little Lady. He has to touch, feel and see it and know that it actually has purpose to him before he would even think about applying himself to memorizing it -- in this case the order of the planets.
Last year, with the Little Lady I just had to tell her that the first letter of each word in "My Very Educated Mother Just Served Us Nachos" would help her remember the order. She said, "Okay. That is easy!" And that was it! She remembered the order of the planets. But, when I told the Little Man that little jingle he looked at me like I was from a different planet. "You mean I am going to have to memorize a silly saying in order to memorize the order of the planets?" I have to admit the Logic in that was totally hilarious!
So, the Little Man did the activity which shows how big or little the planets are in relationship with each other and placed them in order. We started with the Sun! The Sun Balloon is supposed to be the biggest balloon of course! But, I couldn't blow it up any bigger! Then, we did Mercury, Venus, Earth, Mars, Jupiter, Saturn (See the white paper ring around it?), Uranus, Neptune, and there is a little tiny Pluto. (Yes, we know that Pluto is not considered a planet anymore!)
He can tell me the order of the planets now.
Planet Scale diameters of planets---------------------------------------------
Mercury .76 inches
Venus 1.90 inches
Earth 2.00 inches
Mars 1.06 inches
Jupiter 22.36 inches
Saturn 18.00 inches
Uranus 7.74 inches
Neptune 7.8 inches
Pluto .54 inches
I just made them relatively smaller or bigger to each other and followed the chart loosely! It worked!