There are a lot of possible ways to describe a full diaper. A bad one would be, "Rick James is in the house." The problem here is that people will ask for an explanation (Rick James was very funky) and in the process of giving it your older child will learn the word "funk." When he says it, it will sound like something else.
On the other hand, an odd but fitting description is, "She's got diamonds on the soles of her shoes."
My daughter has a distinctive waddle after loosening her load. Maybe you have to be there.