You cannot go wrong, staying at Carmen's place. Especially with a big family! We stayed for 10 days with a family of 6. There was a bedroom we considered the "master, with an attached bath. The 2nd bedroom had a very comfortable queen size bed for our 14 year old and his 8 year old sister slept in the loft above him, in a "twin" (yet wider). Our 19 year old had her own room (twin) with her own bathroom. Our 21 year old had his own room (full) with his own bathroom.
The AirBnb is in a great location with several restaurants right next door, Pharmacy a block away, and the best Gelato in Rome 2 blocks away. We bought a 7day Metro pass and traveled just about everywhere, with that. The walk to all 3 stations was totally doable - 5-10 minutes max to Termini, Repubblica, and Castro Petorio. Everywhere we qanted to go, left from those 3 stations.