|Meconium can stain pretty badly but I guess I was lucky with my twins because we had no meconium staining at all (either that or it sunned out easily when I hung them to dry).
But I can understand not wanting to take that chance so I'd definetly recommend the disposable liners. I'd even double or tripple up on them to be sure since it can seep through. You could even use them in conjunction with fabric liners of some sort to really give good protection. You could even just cut up an old shirt of some kind, anything you don't mind getting stained. And for additional protection you could make the liner big enough that it kind of 'hangs' out of the legs of the diaper, that way there's nothing that can kind of 'slide' off the liner if it shifts...
HTH, congrats on the next little one!