Can I let my baby to sleep in playpen at night instead of in baby cot? Which brand of baby playpen to recommend?

Why not? I bought a cot but rarely use it and bought a playpen for her to sleep in when she is older. Most playpens also come with changing tables and diaper organisers which are very handy and useful. They also have wheels so you can move them around the house easily. Graco is a very popular brand and the pack n play model comes with a bassinet and mobile. Actually, most playpens function similarly. Other brands include Lucky Baby, BabyOne and BabyTrend, among others. Get one which is easy to open and close. A very pretty but tiny playpen is the nuna sena.