IV. The meal - The Mishna Berura writes that a person should be machmir and eat a כזית of bread after nightfall because there are opinions that are you not יוצא the mitzva of seudas shabbos in the time of Tosefes Shabbos.
V. When should you recite shma? You finish your meal and it is time to bench and you remember that you need to recite shma again, do you bench first or say shma first? Both are דאורייתא and both would seem to have about the same frequency. It's possible that you can do which ever you want first וצ"ע.
VI. When should you daven mincha on Shabbos? If you were careful to daven mincha before plag on Friday there is room to say that you should daven mincha before plag on shabbos for the following reason. Since you davened maariv early (before sunset) you defined the time between plag and sunset for that day, Shabbos, as night. Therefore on Shabbos you should daven mincha early before plag. This is a chumra and certainly not required but is something to think about.
All in all early shabbos is a very worthwhile experience especially when you have small children, it allows them to participate in the Shabbos meal Friday night, and it allows us to fulfill the mitzva of tosefes shabbos in it's full meaning. We should just keep in mind the points raised above so that we conduct ourselves according to halacha so that it doesn't become יצא שכרה בהפסדה.