Aww, don’t spoil the fun. One of my favourite bits is when they beg to be allowed to wash it off and run to the bathroom thinking the water will make it better.
But yes, your lotion tip is the one I give too, it works, a bit.
If you’re using toothpaste though, water’s a good idea at some point. As lots of toothpaste has little irritants in it for polishing your teeth which really aren’t meant for down there. This is why menthol rubs etc are actually better, and they’re pretty easy to get.