I love Ivo - both it's sound and it's meaning and I think if you are in the UK then 9 times out of 10 you will get the Eye -voh pronunciation, since similar but more dated Ivor is so well known (so pronunciation wouldn't be something that concerns me). More concerning might be that Ivo's so similar in style to all the other trendy two syllable "-O ending names (Leo, Theo, Milo, Arlo, Kylo...) - but it's not too popular yet, so I'd go for it!
Elliot/Elliot has spelling issues (both spellings are equally popular) and while nice a enough name feels both slightly surnamey and also sounds more overused to me (possibly because there so many girl "Ell's" about -Ellie's, Elsie's, Ella's etc).