Hi P.,
I have a similar situation with my MIL...both of them. My husband's parents are divorced, and all the grandparents was a piece of our daughter's life...ALL THE TIME. No one offered to watch her, thank god. But, we run into issues frequently about "how things are done." My one MIL just needs a confrontation of sorts, it sounds awful but it is true. She actually needs a firm hand before she'll listen. The other one, well we haven't found a perfect way to deal with it yet. She's a wild card. She doesn't get a subtle hint, and any direct communication soon becomes hysterics. So, ultimately, she's manipulated us into never confronting her, without an all out emotional scene. ugh, it's exhausting thinking of it.
I can appreciate what some responses have communicated about, "hey, what's the problem! You're lucky!" However, I'm willing to bet those people haven't had a MIL drive them to tears ona regular basis over not listening to them and undermining them. Also, avoiding situations like this--in the end--is just the thing you NEED to keep the peace. It just becomes too much, too close, to heated. My Mom is that kind of grandparent. Listens to us, praises our parenting style, etc. She spoils our daughter, but is very respectful of it and rarely questions us. So, we don't mind the spoiling so much because we know she's in-tune with what we're doing.
If you can stand having her watch your child 2 days a week. I do believe it is the best interest of your family to keep the peace and compromise. Share your concerns with your husband. Make sure you two agree on the "rules." Then sit down with her, and have HIM explain them to her, clearly and firmly. Have her keep a log of your son's day, as any daycare would do, so you can see how is day is progressing. Then, you can say let's try this out for 3 months and then see how we're doing. Across the three months, just be on top of your communication, and make sure you and your husband are a united front. As for the daycare aspect of it, tell her you think the social interaction is important. That will take the sting out of it for her.
As for her raising your husband, and him being a man you'd want to marry. Well, often our strongest personality assets and our weakest personality defects stem from our upbringing. It's sort of irrelevant that she raised your husband, that doesn't make her an authority, or validate her. The bottom line is that the two of you chosen a parenting philosophy and she can respect it and get on board or not.
As for daycare being a good or bad solution, everyone has a different idea about this. I had to work. I still do. We both do. So, we had to have someone watch our daughter. A Nanny was out of our budget, so we found in-home daycare. For us, it was the perfect solution. More personable, and family feel, more affordable, but more socialization. Everyone has to do what they have to do. I have many friends who ADORE their daycare. Many daycares have streaming webcasts and you can log-on and watch your children. There are pros and cons to both.
At some point, your quality of life and sanity outweigh any money you're saving. You'll know that point. There are many ways to save money, and many things you're willing to spend extra money on because they afford you more of your life back, or they keep you mentally where you need to be. If your MIL drives you nuts, and causes fights, etc. It will not be good for you, your child or your marriage.
Good luck, I know this is hard. There is no "perfect" solution. I hope you work it out soon!