Hello Andrea.
If you sign up for the MLO online synch service (less than the cost of a coffee, files protected by the security of Amazon servers, but with no encryption during transport), then you and your partner can share an MLO file and both make edits to it and check tasks off.
MLO is very customisable, so you can use flags, categories or text tags to highlight which tasks are for your partner to do... or just stick them all in a particular folder for him. You could then set up customised views for each of you to see just your own tasks.
Welcome to the forum.
Stéphane