i can understand how crabby kids would be when dinner is between 6:30 and 7pm (which ours often is too). if you give them a small, protein-rich snack immediately at pick up time, would their appetite for dinner (30-45 minutes later) really be ruined? that's not the case for my kids, but i understand they're all different.
i have one "good" eater and a picky one; however my "good" eater is vegetarian and they give him a pb&j like every day for lunch. i mean, he eats whatever else is being served, like if there are potatoes, veggies, fruit, muffin, vegetable or tomato soup . . . but sometimes the meal is predominantly meat and i know he's just eating a sandwich, so i'm trying hard to balance that out with our meals at home. however, i also really want/need it to be quick and easy.
i feel like we get our "reconnection" time in the car. we talk about their day, what we're doing that night, and what else is coming up in the near future. once we get home, they want to play with their toys or ride bikes/scooters if it's nice out, so that allows me to get dinner rolling. if they are grumpy and not playing well (so i have to stop what i'm doing to split them up or whatever), um, i will probably put on a video. i know. but we do what we have to do, right?
my mom has been sweet enough to give me some frozen food (that she cooked) which is easy for me to heat up. i've never had a microwave until me & stbx separated, but now i think it's awesome. other quick stuff i make: pasta (i get barilla plus, because it has protein) with a really simple sauce or primavera or just oil and a little cheese; breakfast-for-dinner kind of stuff; soup, my boys love soup. we're in a temporary living situation but when i get back to my kitchen, i'm super excited to start using my crockpot a few days a week, making big batches and freezing. that way dinner will either be ready when we get home, or will be waiting in the freezer to be nuked.
i don't know what i would do without snacks, though. sometimes i have something in the car for them, or sometimes i give them a snack right when we get home. other nights they're less hungry - once your kids get more accustomed to the food at daycare, they will start eating more. i forgot, i was going to say that about my picky eater, it just took him some time.
if your kids are having tantrums because they want/need your attention, how about letting them help by setting the table or doing other chores? or just sitting on the counter and talking to you while you cook?