How to find opportunity cost if each choice has more than one important effect?
Note that as a rational agent you will have preferences on the set of (wage, free time) bundles. Your own answer suggests that these two "goods" are perfect substitutes, but this is not the general case. If your preferences are given by a utility function you can calculate the utilities for the three bundles in your choice set and then proceed in the way you indicated, measuring opportunity costs by utils foregone.

Alternatively, you can for each of the three bundles find a respective indifferent point at the maximal-free-time line in the space of bundles (corresponding to zero traveling time) and compare the wage levels of these points to get a monetary measure of opportunity costs. This corresponds to converting the traveling time contained in each bundle to some wage loss which you would be prepared to face if traveling time could be eliminated from the respective bundle. (If your preferences happen to be quasi-linear in money, this amounts to calculating your willingness-to-pay (WTP) to avoid traveling time, but in the general case this WTP need not be independent of the wage level.)