How to raise grateful children

Mom of three boys 4, 2, and 4 months. I grew up very differently very strict wasn't allowed to show emotions and express my feelings also physically and mentally abused. I was always made to feel like I needed to apologize for everything and I was just grateful when I wasn't. That being said I'm raising my boys very differently. I'm not necessarily a gentle parent we do time outs and I'm not an angel I have raised my voice. My background is early child development and special education and was a former teacher. I should know how to handle this lol but being a parent is different.

My kids are constantly telling and yelling at me and disgruntled with every day things they should be grateful for. I'm working hard at listening to what they want/need but what's happening is it's continuous complaining melt downs. I'm teaching them how to manage feelings when they are in meltdowns but with three kids I'm spread thin and honestly I just feel like I'm being yelled at all day.

Yesterday for example my oldest was so excited for Valentine's Day. I had made breakfast but wasn't his heart shaped pancakes he had requested. He was angry although I decorated our home he didn't have balloons. He was then angry the garage wasn't decorated or out SUV. Every meal we sit as a family they loose their minds it isn't exact how they want something. We have a rule to take no thank you bites and then be done but it's turned into all out hour long fights over how I don't make what they want. My kids eat really well and do try food but the constant complaining of what I'm cooking while I'm cooking it while dinner and even during clean up is exhausting.

I try to create moments of my children getting one on one time we don't do much screen time and we are super active outside and with other kids. I'm trying to listen to my kids feelings but I feel doing so is almost making the situation worse as they tell me continuously how upset they are over everything I am doing for them all day every day.

My husband isn't as patient and will snap at them. I have what feels like conversations multiple times daily of gratitude gratefulness and even fairness. We are Catholic home it makes a difference but I'm looking for insight how to curb the fits fights and complaints. It's sucking at the joy for me and I don't want to be complained at continuously for my good intentions of creating a wonderful childhood and home.