The possible results are as follows: (A means up, and B means down, including the order of consideration)

AAA, AAB, ABA, ABB, Baa, Bab, BBA, BBB (8 cases)

Only AAB and BAA and ABA are two positive aspects (three cases).

There are just two heads up =3/8=0.375.

Probability of no head = 1/8.

The odds are =3/8+ 1/8=0.5.

So it's fair