I am not keen on Magnus. Love Otis and Theo. Like Marnie for girl but she will always have to say Marnie with a IE when spelling it :-(. What about Orla. ? My boys are Joseph and Leo. Whatever you choose will be great for your child. Good luck
Dislike Magnus (it's just ugly, sorry). Finley and Finn are both great. Theo is OK. Otis sounds like a twat (I really don't mean to offend anyone, but if I met a teenage or above Otis then that would be my immediate thought (I appreciate that this is entirely my own prejudice, again, sorry)).