Do a search for threads/posts about taking classes like these over the summer and see how many of them did well. You'll see how right most of the people in this thread are.
I took my intro E&M over the summer over six weeks, and while it was easy, I didn't retain anything about it. The professor clearly made it easier than it should have been, and all I learned to do was use an equation over and over.
The reason I didn't learn the material and others here say YOU won't learn the material isn't because it's necessarily super hard conceptually, but because the reason people get GOOD at Calculus is because they grind problems into the ground for 14-16 weeks, as opposed to 6-10. It's like doing reps in the gym, you may look cool in your head doing curls or press really quickly, but you actually strengthen yourself when you do slow, controlled movements that get a proper range of motion. Your brain works in a similar way. When you stretch out the time you learn the material your brain gets better at processing the problems, and when you get to Calc 2 or 3 and you have to churn out a long derivative it takes way less time because you had a full 50-100% more time to study a section of the book (Supposedly you think you're good at math, so do it here).
Also if your parents are telling you to do this they clearly have an unhealthy image of what a good student is and you should not be taking advice from them. Just because they're your parents, and even if they've steered you right in a lot of ways, doesn't mean they're infallible.