Finally starting our landscaping!!! i have a ?

[MissSJ]

We are finally starting our landscaping but first I have a question for the toxin-smart MDCers. We will have a 20X30 foot play area filled in with pebbles. To section off the area we are thinking of using railroad ties (the ones you get from Home Depot that aren't "greased"). I just want to make sure they aren't treated with anything that will be harmful to either DS, particularly DS2 who is just starting to walk and I know he will be holding on to them a lot (not to mention he is in the mouthing stage - everything goes in!). If the ties aren't a good idea anybody have any inexpensive, easy to install alternatives?
Thanks
SJ

[SleeplessMommy]

There are recycled plastic landscape timbers available - these will be 100% non-toxic. Also, you may want to look into getting truckload of shredded tire mulch - very nice for a play area, and lower cost than pebbles.