I really wouldn't be planning this far ahead. Assuming the situation in Portugal is similar to the UK, matches can and will be moved to work around tv schedules and month or two before the game is played. It could simply be a change of kick-off time but the match could also move from Sunday to Saturday or even the Friday.
Yeah appreciate that. If that's the case then that's fine, we'll be there Saturday and Sunday. If it's Friday then will just have to suck that up and enjoy a weekend in Porto. Can't not plan it in advance with people's diaries/commitments/childcare help. And if it moved to Friday we couldn't go anyway as there's no flights.