Delete the comma after excitedly or add another one after jars. (The phrase with their fishing nets and jars may or may not be a restrictive clause, which is why the commas — two or none, but not only one — may or may not be needed, depending on what the writer intends.)
I recommend changing towards to toward.
I added a comma after day for clarity. (The sentence is not compound, but the comma keeps the two things the character wished from getting mixed up/blended together.)
He had memories of the five of them running excitedly, with their fishing nets and jars, toward the pond where they knew a bounty of tadpoles awaited them. How he wished they had known just what else was waiting that day, and that he could say the memory was a happy one…
I’ll allow the ellipsis at the end to remain, since it seems to fit with the “little did they know” tone of the second sentence. (Melodrama, much? *shakes head*)