The first option is fine as long as there not trying to min-max a multiclass build. If its pure RP all the power to him. But I would keep the save the same

As for the second? Mmmm might be a little to much maybe instead find out what pact they are going to choose and look at the list of extra spells they get and tact on 1 extra spell (your choice as the DM) to that list to help augment their theme and give them a little more to work with.

And if your party winds up not taking many short rests consider the rule we use at my table for a warlock. Which lets him convert his HD into one extra spell slot once per short rest.

Example

If the warlock has a lv 3 spell slot he has to spend 3 HD to create his bonus spell slot. Or 5 HD for a lv 5 spell slot and so forth.