Having Sex with One Wife While the Other Wife Is Watching

I married my husband six years ago. We dont have kids because I am unable to conceive a child. Doctors told me I am permanently infertile and medicines are useless. My husband is ok and he wants to have kid. About two months ago he married another woman. My husband is a very kind man.even after his second marriage his attitude towards me is good. My husband's second wife isalso a nice lady. She is very kind to me. We live in a very small house with one bedroom with attached toilet. The kitchen is located outside the house so nobody can sleep there because it is not safe to stay outside at night. Similarly nobody can sleep in toilet. All we have is the bedroom which the three of us share. My husband is a poor man , neither he can buy anew house nor he can afford the rent. we have arranged for a seperate bed. So now for onenight my husband sleeps with me on double bed while the other wife sleeps on the seperate bed and the other night she sleeps with husband while I sleep on the seperate bed. Me andthe other wife daily switch places. We dont have any problem with that because It is the only possible solution. We donot ask for seperate house because both of us know that our husband can not afford it. Our husband has promised us to provide seperate homes whenever he hasenough money. Now my question is that it is ok for my husband to have sex with one wife while other wife is watching ? I know that it is not ok to look at other woman's awrah ( fromnavel to the knees ) but if my husband covers himself and the wife with a sheet of cloth whilehaving sex ? I know that it is unlawful to disclose the marriage secrets to other but there is a difference between ordinary public and wives. I know what he does to other wifeand she knows what he does to me.  Under the circumstances this is the only possible solution for us. Can we both have sex with our husband simultaneously if we both wear such clothes which conceal our bodies from navel to knees but allows our husband to have sex with us? In this way we shall not be able to see each other's awrah.