@Fei3 You are opening yourself up to a lot of possible problems. I was looking for a picture of your stairs but you don't have any (you almost have more flower/fruit pictures for your listing than actual house photos). There aren't many baby gates that can be installed without damaging either the wall or the banisters. Pressure mounted gates are dangerous because they can easily "pop out" of their place ... plus I really have no idea how your guest would know what kind of gates they could bring without seeing any pictures (unless you sent them some in private). I installed a lot of different gates into door openings, bottom and top of stairs and it involves a lot of measuring and careful instal as not to damage anything.
And what if a gate isn't secured, a child falls? They can blame it on your house that they were not able to install it properly. You are openning a can of worms right there, just don't do it. It's the parents responsibility to watch their children. Hotels wouldn't install gate on request either.
Unless you have a place that you especially cater for small children (some hosts do) and you have a properly installed (meaning with screws, etc.) gate I'd not let anything else in there.
