I just took a look at the benchmarks and indicators for science in Ohio. In grades K-2, students should really be able to ask a question. Here are the benchmarks for first graders in the area of Scientific Inquiry:
1. Ask "what happens when" questions.
2. Explore and pursue student-generated "what happens when" questions.
3. Use appropriate safety procedures when completing scientific investigations.
4. Work in a small group to complete an investigation and then share findings with others.
5. Create individual conclusions about group findings.
6. Use appropriate tools and simple equipment/instruments to safely gather scientific data (e.g., magnifiers, timers and simple balances and other appropriate tools).
7. Make estimates to compare familiar lengths, weights and time intervals.
8. Use oral, written and pictorial representation to communicate work.
9. Describe things as accurately as possible and compare with the observations of others.
What really leaps out at me is the emphasis on understanding the beginning of the scientific method: ask a question, and make a prediction. If the display is more of a model (tornado in a 2-litre, volcano, etc) it's not allowing the students to experience asking and answering a question. (You sounded very excited about a "cool" display of earth's layers, but is there really a testable question involved?)
Here is a link to Florida's standards for PreK-2.
"In all our woods there is not a tree so hard to kill as the buckeye. The deepest girdling does not deaden it, and even after it is cut down and worked up into the side of a cabin it will send out young branches, denoting to all the world that Buckeyes are not easily conquered, and could with difficulty be destroyed." - Daniel Drake, 1833