I would hate to have either parents or PiL in there - I don't really want DH there either, so I'd say no way! If your FiL so desperately wants to watch a birth can't he get a birth video - I'm sure your antenatal people can lend you one. That way it's someone who's OK with other people watching her give birth and you don't have to have your FiL there if you don't want him to be.

And it's so nice of your SiL to ask you to do something that she just can't possibly do now - well, it's not too late, so if she wants to make her dad happy and watching a birth she can get pregnant again. I think her asking you was unacceptable TBH, though you might not feel that way. I know if anyone told me my FiL wanted to watch a birth, could he see mine, everything would just hit the fan. Same for my dad, or my mum, or my MiL. I love them all, I just don't want them there! But it's your decision, I just wanted to say there's no way I'd have that and I'd be really annoyed at the person who suggested it.