I may have shown this too you before, but here is a matchup "chart" if you will that displays matchups relative to Snake for his disadvantaged matchups, which are The ones you mentioned, MK included. After a summary, it will list a score. You want the highest score that you are comfortable with.
Olimar-has +2 against Pika and DDD, -1 vs MK. (3)
Pika-has -2 vs Oli, worse than that of Snake, +2 vs DDD, even with MK (supposedly). (0)
MK-even with Pika (supposedly), +3 vs DDD, +1 vs Oli. (4)
Snake-has -2 vs Pika, and -1 vs all other mentioned chars. (-5)
ICs- -1 vs MK, +3 vs DDD, +1 vs oli and pika. (4)
Diddy- -1 vs MK, even vs Oli, +1 vs DDD, pika. (1)
Falco- (0) (No summary)