Eliska's place was ideal for our group of 9 guys, a larger group would still be fine. The apartment is just around the corner of the old town. Almost everything you would want to see in 2 days of Prague is in walking distance (less than 2 km). Only down side was the condition the apartment was in, but if you don't expect too much, this is also fine!
Communication with Eliska and her mother went very well. We came a bit too early (because or bus arrived earlier) and we could also stay a bit longer before checkout. This was no problem at all.