You're welcome Tiffany!
Glad to have been of help.
Well, some areas of NJ are more prone to higher radon readings than others, but even in towns where elevated radon readings may be rare, an occasional reading can come in at over 4.0.....
I wouldn't worry about it as long as you have a reputable mitigation company do the work.
They can also explain the process and reassure you that after the installation, radon will no longer be an issue - your toddler can safely play in the lower level!
I have a 3 yr old granddaughter - so I can empathize with your concerns