lol, no.
छत is ROOF, and also terrace due to the structure of lots of Indian houses, yes. But if you remember it as roof, you won't confuse it with patio :)
Firstly, it's 'my' rather than 'their'; and it does need to be 'on' the terrace, not 'in'. 'In' is like actually inside something, अंदर, you can be 'in the house' because the roof covers you and the walls surround you, but the terrace is merely beneath you, so it's 'on the terrace'.