That is a nice use of motion tweens! It compliments your art direction, which is endearingly simple, pretty well! Also, the subject matter is rather wholesome!

Now, my biggest concern is that the boop isn't conveyed clearly enough. Since the arms are greatly stylized and the perspective is a little off on them. They appear that they are emerging from the ground instead of from an upright torso. Also, I think a cute sound effect (i.e. a slight squeak) will provide a better clue that you're not just squeezing their muzzles.

By the way, care to try more ambitious animation techniques in the future? Motion tweens have their place, but they only go so far before you need to create several frames by hand.