If you figure it out, let me know! I was a SAHM for 5 years, and I never figured out how to keep the place clean for more than a few days. My kids are 6 and 3, and I believe it will start to get easier. My 6 year old is much better about putting things away and doesn't make nearly the messes he used to.
I think it's unfair to ask the grandmothers to play housekeeper as well as nanny. It can be hard enough to keep up with the two kids, they don't need to be concerned about cleaning along the way.
I'm working full-time now, and my kids go to daycare (well, aftercare for the 6 year old). One of the reasons I chose a daycare center was so that my house wasn't getting messed up any more than absolutely necessary. It's still a lot of work to keep it clean, and I don't really enjoy spending my free time cleaning when I really want to spend it with my kids. It's hard to balance the two, but I do my best.
When your kids are this age, they create messes. In a few years it will be more realistic to keep things in order. In the mean time, try to embrace this time for what it is. A messy house isn't the end of the world.