How do you say thank you?

The babies have regressed in their sleeping abilities lately. Richard and Audrey did the same thing, so it's not totally unexpected. It's just harder to get up every 2-3 hours through the night when there are two babies instead of one. So, I'm tired. Very tired.
My mom and my sister are my life-lines. I count down the minutes to when they'll arrive. I know that once they come, I don't have to bounce two babies on my own while trying to get a two-year-old to the potty. I might actually get a nap so I don't have that fuzzy zombie feeling all day every day. I know my family will be fed a meal that consists of more than just sandwiches or processed foods. I know that someone will play patty-cake with Marie and Peter and that someone will read books to Audrey. Someone will watch Richard play Mario Kart and cheer him on. Someone will listen to me talk and I don't have to just have conversations about why we need to share, be nice, clean up our messes, and be respectful. I know someone will bounce babies so I can play games with Richard, read books with Audrey, and, heaven forbid, do something for myself like exercise. I know I'll be able to exercise continuously rather than stopping every 5 minutes to help someone. I know my kitchen floor that wasn't mopped in two months will finally get cleaned. I know I can go to the grocery store or some other store without four children.
So, how do I say thank you for all their hours of service? How do I truely express my gratitude to those who selflessly give of their time week after week? I would survive in the basest sense of the word without them, but they allow me to actually live. How do you pay back their kindness? I feel like just saying, "Thank you" is not enough, but since I haven't vacuumed my house in over three weeks, I don't have a lot time to create something. I'm not even sure what I could create that could do my feelings of gratitude justice.
I also need to recognize a member of my ward that takes all four of my children once a week for a couple of hours so I can run errands that are more lengthy. She doesn't even have a vested interest in me and yet she serves me weekly. She told me she was watching my kids and didn't wait for me to ask for help.
So, while I sit here typing, bouncing one baby on each leg and talking to Audrey about macaroni and cheese and watching "It's a Small World," I want to publicly thank my Mom and my sister. They are angels. They don't have to do what they do and yet they feel I'm important enough to make sure I have sanity. Thank you. Thank you. Thank you.
I know my other sisters would do more if they could. I recognize that. However, I have been so overwhelmed lately that I just need to let the readers of my blog know who really keeps me sane. I wish everyone had as much charity and love as these women in my life.