WSP is having a sale going on right now and many of their M&P bases are reduced in price. They also have free shipping for orders over $25.00. The handling fee of $5.95 is less than the USPS Priority Mail they are going to use to deliver it to for the order I just placed. And location-wise, they are in Ohio, much closer to you than Bramble Berry, which is Bellingham, Washington (and a bit too close to the wildfires in Washington for delivery truck drivers, IMO.)
PS: It's fine to make MP soap, and right now with you son, if you feel safer avoiding mixing your own lye solution and all else entailed in making soap from scratch, that's what you should do. If later on you feel like making soap from scratch, we will be more than happy to help you through that, too.
There are many soapers here who have used & still do MP. The more experienced ones will be along sometime soon to provide you with recommendations, I am sure.
Edit: This is a mild non-detergent MP base on sale at WSP with reviews saying it has good lather:
Crafters Choice™ Detergent Free Baby Buttermilk MP Soap - 10 lb - Wholesale Supplies Plus
But there are many others as well, you'll just have to read up on them and perhaps someone here who has used one you are interested in, will be able to answer your questions.