Likelihood of getting pregnant first month TTC

Barbara • 28 and pregnant with baby #2!
My husband and I are going on a cruise in September and he wants to wait to start trying till after so we can really enjoy ourselves, but I want to start this month, what's the likelihood that we would get pregnant on the first cycle?! 
My thought is even if I get pregnant before the cruise what's the worst that could happen, just can't drink at all? Doesn't bother me! 
Also I signed up to run a half marathon in October, can I do this while being 4-10 weeks pregnant?