Caroleesmom, I could have written your post fifteen/sixteen years ago. My kids are now 19, 17, 16, and 5 (so I still have days like that with the five-year-old, who also loves to collect things ;-)).
So much of your post stuck out to me, but the main line that tugged at my heart was this: "How do I make myself happy and make my kids happy?"
If I could tell you anything, it's this: Let go of the expectations you've put on yourself (I know -- easier said than done). I think we all have an idea of what a perfect mom should be, how a house is supposed to look, that dinner is supposed to both taste AND look good, and that the outside of the house should be the envy of the neighborhood (or close).
I've learned something in my years as a mom, and it's this: Our kids don't remember if the living room was cluttered, if the bills were paid, if the meals were perfect, or if the yard was mowed. But they do remember people. They remember their mamas, their daddies, their siblings, and other important people in their lives, and events associated with those people.
You sound like a wonderful mom. Your girls will remember that you spent time with them outside, that you took them places, and just that you were with them so much. When they're grown, their memories will be of YOU, and that's a great thing.
We hold ourselves to such high standards, don't we? And you're in a tough time -- it's not easy raising little ones. I had three under five at one point -- I was a wreck back then. I wish I'd known one piece of advice, and I'll give it to you: Give yourself a break. Your home will be messy, your kids will drive you crazy, your husband may even seem like he's completely out of the loop and not helping. I wish I could have accepted that -- it would have lowered my stress level in a very big way.
You sound tired, too. (Understatement, I know -- most moms of young ones are physically, mentally, and emotionally exhausted. I was.) I'm sure you've heard this, but you must make time for you. You have to have time to rest, recuperate, regenerate. Hire a babysitter to come in once a week and watch your girls so you can go to Starbucks or go shopping...or so you can just get a nap! Try to have a regular date night with your husband so you two can reconnect. And make sure you're getting the sleep you need at night -- I definitely could have improved in that area (still could).
I so feel for you -- I know it's difficult. But hang in there; it does get easier. As they get older, they'll be able to do more for themselves and will play together better without so much drama.
You're doing a good job, mom. Just thought you needed to hear that. :-)
PS: It's okay to "park your butt on the couch and let them play" once in a while. ;-) (Especially when you're tired.)