Forgot to mention...I have been told that using black plastic warms the ground up a bit more, so you can work it up to a month sooner. Not sure it is true, but I am giving it a shot.
Yes on the black plastic. I have one bed covered as we speak trying to kill of the crab grass that has invaded. Normally in Sept/ Oct I go to sis in laws and load up on horse manure then spend all fall and winter turning in over. This year I got zip. The tractor was broke and I was way to chicken to enter the horse area on foot. Most of my beds are ok but I needed just a bit more.
your onions should do great in tubs. Last year was my first year with onion sets. I did ok but as they matured the gophers helped themselves. As usual. This year they will go in a raised bed.
I think the peat moss in the lasagna garden is to retain moisture. I think if you stay on top of the watering you should be fine.
I live in chillywilly Canada lol now heres my little explanation on plastic to warm the soil which I'm sure you'll enjoy..
Most people here don't plant Tomatoes until May/June because of the chance of frosts killing the baby plants off. I planted mine in April LOL I put up a "raised bed" around them and put 2 pieces of wood staked into the ground in the middle of the bed. On nights I knew it was going to be cold or below freezing, I watered the bed in the morning, and stapled 6 mil clear plastic over the bed and left it all day. During the day it would steam up and create a nice little hot house, and it kept its heat overnight.
In August when people were confused that their tomatoes were tiny and had little fruit, my tomatoes were as tall as my waist (i'm 5'10!!) and we had so many tomatoes we had to feed to the chickens near the end. I had over 150lbs of tomatoes. I couldn't even gift them as fast as they were ripening. I made enough tomato sauce for the winter which has been used in chili a lot here.
Looks like you are off to a good start with the garden.
Thanks for sharing the pictures - helps me daydream of our garden as I sit in the freezing cold temps with snow on the ground and snow in the forecast for tonight.