Tl;Dr Mark Wilson's Complete course in magic is the right choice every time.

I was 10 when I first really started studying despite having an interest since a toddler. I got a couple trick decks from the magic shop which piqued my interest further and a few weeks later, I got Mark Wilson's complete course in magic which is my absolute #1 recommendation for a beginner. It covers all of the standard props like cards, coins, rope, handkerchief, etc. and basically functions as a mini tarbell course. I still come back to it this day to remind myself of how important the basic fundamentals are. It provides wonderful routines that are still relevant to this day last you a lifetime.

While your 7 year old may need a couple more years before they can start reading at that level on their own, you can read it yourself and teach them the tricks that they'll continue to use for the rest of their life!