The place is superb. We stayed with my wife and kids (2 years and 9 months old). They provided a high chair and crib.
The flat is on the 3rd or 4th floor so we left the push chairs on the first floor... It's secure. Anyway, we recommend you don't bring push chairs since Lisboa is full of hills.
The place is managed by a company. They were available every time I contacted them. One time Internet got disconnected and they send someone at 10pm to check it.
If we are back in Lisbon we would choose the same place again.