New to teaching and looking for advice

Hello, I am a college student looking for help in educating two kids through math in first and second grade. A long-time friend of mine has two kids who are driving her crazy and she needs help getting them through school. I offered my help and I am both excited and nervous to give this new road a try.

I am here to in hopes that some people could give me some advice on what a proper course of action should. I have some general information to hopefully fill in any questions required to continue:

• The ages are six and eight.
• 6-year-old is a boy in the first grade.
• 8-year-old is a girl in the third grade.
• My job is loosely defined but my main mission is their success in math.
• We will likely be working together in person and not through zoom.
• I will have them 4 days a week for an hour or two.

I have some questions based on this information that I hope can be answered here:

• Is Khan academy the right resource for this situation?
• If so, how can I utilize it to its full potential?
• What are some basic steps I should take before getting started?
• How can I teach two different grades at the same time without too much difficulty?
• As someone who is new to this, does anyone have any advice for me?

Thank you so much for taking the time to read this. If you can help me, I would greatly appreciate it and would love to ensure that I do a good with these kids.