What is the tiny-hand most-friendly sets to migrate from duplo to lego? How do I migrate a kid who's taken an interest in lego (with a preference to minifigures) from their current duplo collection?

I'm tempted to buy just mini-figures, but have seen some "mini" sets that are mini-figure heavy like The LEGO® Batman Movie The Joker™ Balloon Escape: 70900 set.  The problem is that these sets typically contain many small parts that is likely to get lost, or frustration ensues because building or taking them apart is difficult. (Funny enough minifigs aren't taken apart as you'd think...)
As a conservative approach I would suggest the LEGO Juniors series which has cars and other sets and that are easy to build. 

However, from first hand experience I can tell that kids learn quickly. Even if reading instructions is too difficult, playing with regular LEGO parts will soon be a lot of fun.

Besides : Losing small parts will be an issue with each and every LEGO set. Maybe you could consider buying used sets or even used bulk LEGO. 

EDIT: LEGO Juniors is now called 4+, but it is the same product line.