The answer to your question would be that the simple subject of the sentence is the following one: Michelle and Suri.
The subject of the sentence is the person, place, or thing that is doing or being something. If you find the verb, you'll be able to identify the subject. Ask the question, who/what (verbs/verbed)? The answer to that question is the subject. In this case, the question would be as follows: Who likes to shop at the Lemon Grove Mall? Michelle and Suri.
