Hi Dina, don't scrap your tickets. In your situation, I'd take the elevator to the second level and then have your husband and son immediately get in line to buy tickets to the third (summit) level. With your pre-purchased tickets, there should be little to no wait time to get to the second floor. The couple of times I needed to buy an additional ticket to the third floor, the line was very short (like 2 people in front of me). I think the additional ticket was about $6.
I don't have an issue with heights (it's enclosed spaces that bother me!), but my friend does. We visited the Eiffel Tower in May 2014 and had tickets to the summit. We got to the second level and he said that he couldn't go any higher. I pointed him in the direction of the gift shop and snack bar and went to the top by myself. By the time I got back down to him he was fine. We did another trip in May 2015 and he insisted that we both go to the top. No problems at all. My point is, if it makes you uncomfortable, don't go to the top. No reason that others in your group can't do it while you're wandering around the second level.
I really hope you have a great time in Paris. The Eiffel Tower is amazing and breathtakingly beautiful when it twinkles!