If they are found guilty, they deserve the highest sentence allowable.
That said, this whole story doesn't ring true with me. The only thing that has been consistent is the fact that there is a dead baby, and someone shot the poor little thing. The mother seems... off. If I'd just seen someone slaughter my baby, I wouldn't be giving long, rambling interviews within hours. Everything she said seemed so practiced, so nonsensical (the way she made a big deal of running into a driveway with her baby, after the perps had left instead of screaming for help, for example). She seemed more nervous than griefstricken... then again, people deal with grief differently.
All I know is that when I saw her, my brain whispered "shades of Susan Smith." If the police can't find the murder weapon and tie it to their "suspects", you can color me skeptical about the entire quick-turnaround arrest based on... well, based on nothing that's been made public beyond they fit the descriptions.
Yeah, I'm cynical. I know. But I'll wait and see what happens on this, because I'm not getting the "aha, justice will now be done" vibe.