I find poplar very hard to stain evenly with a dye - I find it tends to blotch. What I would probably do it put a base coat of dewaxed shellac on it and then add the color in the finish until I got the color I wanted, then do a final coat of clear (I'd spray all of this). The green of poplar will turn brown after a period of time in the light so plan for the color change.
The other thing to do is to use paint. There's nothing wrong with painted furniture - and you can do some very interesting things with paint and patterns, especially for kids. You can paint some of their favorite characters on the dressers, or do some bold contrasts between the case and the drawers. After all, it's poplar and it's for kids. Let your imagination run wild. You can always paint over it.
Go into the world and do well. But more importantly, go into the world and do good.