We don't go out. Or put lined splash pants on them. I have used the exersaucer or a playpen on my deck for non walkers. I also sit on the swing we have and hold them on my lap as much as I can.

I wait till the end of the day to go out and the dew and dampness has worn off by then on a normal day. I only have under threes so we can be just as active if not more so in the house than outside so I don't worry about it.