We had 3 kids and my mum come and stay in our 3 bedroom unit. We put DS on the floor in our bedroom with the mattress off his bed - DD2 was in the cot, also in our room, and DD1 stayed in her room. Mum stayed in DS's room on a spare mattress from my aunty's house. Was a bit squishy in our room, but we managed!!

Congrats on the house