As far as I`m aware, the Plastikote should say on the instructions that it`s paly safe or kid safe....or something like that. If in doubt consult the Plastikote website?
I`m not sure i would even bother with Plastikote and just use the pine without coating it, although I imagine if it`s peed on it might stink in no time!
That`s probably the downside of wooden accessories, but I prefer wood to plastic as it`s more natural if chewed.