That should be possible. I don’t know the Mini MPK3 but from what I’ve read it says that the pads can be configured to either send note or control change or program change info.
If you assign a pad to send a control change message say midi_cc 7 then you can detect when this happens and use it to play a Sonic Pi Sample. I can do something similar with my rather ancient M_Audio Oxygen-8 keyboard which has rotary knobs that can be assigned to midi-cc signals.
live_loop :msample do #play sample according to triggered control change
cc,data = sync "/midi*/control_change"
sample :drum_cymbal_hard if cc == 7
sample :drum_snare_hard if cc == 10
live_loop :mnote do #play note
note,vel = sync "/midi*/note_on"
play note,amp: vel/127.0
This simple program would play notes from the keyboard, but also respond to control_change signals 7 or 10 (adjustable) to play samples
If you can program your akai to assign two control channels to two of the pads you should be able to use this. If it is a pad then it probably sends data in the range 0->127 depending upon how hard you tap the pad. You could amend the program to respond to a certain value say > 80 using
sample :drum_cymbal_hard if cc == 7 and data >80
sample :drum_cymbal_hard if cc == 7 and data ==0
which would respond when the pad was released.