Simon Says: potty

Andrew and I spell everything these days to talk in "code" around Simon, but it looks like we need to figure something else out...

Me (to Andrew on a walk with Simon): When we get home we need to see if he needs to go p-o-t-t-y.
Simon (who likes to "hold it"): I don't want to go p-o-t-t-y.
Me: Do you know what p-o-t-t-y spells?
Simon: potty.