Final answer:
The most concise way to rewrite the sentence is: "The children planted trees that grew three feet over summer vacation," as it maintains all the key information in a succinct manner.
Step-by-step explanation:
To rewrite the sentence in a more concise way without losing important information, the most effective choice is: "The children planted trees that grew three feet over summer vacation." This sentence retains the crucial details about who planted the trees, the growth of the trees, and the time period during which the growth occurred, while eliminating any unnecessary words.