I'm confused and torn on what to do here....?

My family and I are staying with my sister and her family presently as we speak... thanks to a great supportive family I have! We have plans with them as far as the future goes... in the near future (november hopefully) to all sell the house and get a bigger house or a duplex. Which is really cool because it would be nice for my children and my sister's children to grow up pretty close! Anyhow, in the meantime, there is this house across the street for rent with option to buy.. now i am not reallly wanting to buy due to our future plans. Now, here is where the confusion comes into play.. my sister is really cool with it and thinks i should go for it.. BUT in the longrun, i feel if i do make that choice then it might cause some conflict with my sister's husband because he likes the fact of all of us living together. Which i do too but i also would like for my children to have a bed to sleep in at night. I'm just looking at it like (we will be across the street & we have more room!