You'll be fine with the 50 & 100, that said on a crop you might want a bit wider than 50 for some stuff I suppose but can't really see what you'll gain waiting for or getting the 17-55. 24-105 should be more than wide enough for anything you'll shoot.
Shoot lots of details with the macro lens, fingers, lips, feet they'll never be that size again. Shoot some with a favourite teddy, it's cute but it also adds a scale reference when they look back it reinforces how tiny they are at this point.
Don't try to be too fancy there's lots of newborn guides focus on a couple of simple lying poses. If you have a nice basket or similar it's great for getting some on their back fill it with towels and a nice blanket on top and some side lying poses. You don't need fancy posing bean bags or the like but something to raise them slightly and keep them comfy is great, the main cushions off a couch or similar is excellent with a rolled up towel to prop them up if needed. If your posing them on blankets make sure to smooth them and pull them taught whilst photographing they can be a pain to fix in post. if there hands are in the shot try to spread the fingers out, rub your hands to warm them then gently massage them till they settle. Go really slow when your settling wee one in any pose as long as you go slow and gentle and don't get stressed babies are usually very compliant.
If using flash use biiiiiig soft source so ideally bounce it off a wall or through a sheet or diffuser and add a reflector or sheet to fill shadows if needed. If shooting natural light get as close to window as you can.
Get low and close when you're shooting, keep the room warm and get a white noise app on your phone, I use
white noise baby on android which is free, it's supposed to help them sleep, not sure it does but it covers silences and makes pops and clicks from gear less likely to disturb the wee one.
If they have dry flaky skin a baby wipe dabbed gently will save retouching and keep lots of baby wipes handy for other issues. If you pose them nude you will get accidents.
oh and if you want some nice soft large blankets for shooting on bm bargains usually have a decent range cheap and a couple of a clamps and dining room chairs will make them into a nice seemless background.