How to tell my mom that her home is to gross for my son to visit?

I understand your concern. I would be tactful You can tell her: "I love you mom but, your house is dirty enough where I cannot allow my children to be there." If you can keep your house cleanfor extended periods of time, we can re-visit this situation but, right now I as a mother have to protect my kids. I mean it doesn't need to be sterile and I don't think that is your point. I had a S-I-L and there were paths everywhere, dishes piled in the sink for weeks, garbage piled and overflowing (in a 33 gallon trash can, not the kitchen sized) I felt dirty every time I went there and my ex and I would shower after we got home. ---we didn't have any kids though.