It depends on the snail. Your mystery snails are usually apple snails (www.applesnail.net). If you can tell the difference, P. Bridgesii are ideal for a planted tank. Cana's aren't plant friendly but are still technically apple snails. There are ways to tell them apart.
Aquabid usually has a number of people selling the snails and/or egg clutches. I have dealt with Ijedic with good results (She knows what snails she has, has a variety of colors, and is generous with extras).
And...hopefully you don't have any loaches as they are notorious escargot lovers.