Somewhat new to serging...what thread do I use for this?

[gwen's mom]

I am making Christmas dresses for my nieces-the top is stretch velour, the bottom is satin. So, I was thinking that it might be just as easy to serge the stretch velour. When I sew diapers with stretchy fabric I use woolly nylon. Is that what I should be using for these dress tops too?

Thanks!