A little physiology:
Mare centaurs have a natural breeding season. Increasing daylight stimulates receptor centers in the brain, which in turn trigger the production of reproductive hormones. These hormones initiate the pattern of regular periods of 'heat", or estrous, that characterize the breeding season each spring. These periods continue throughoutthe summer, and cease during the autumn.
In Alidor you are past the breeding period so, well... Offspring are not possible at this time of the year. As for promiscuity, I figure centaurs are like dolphins and since you are now considered part of their group, you can partake in group activities. I supposed they are just as curious as you are, so if you want to James T. Kirk a centaur you could. If your relationship lasts to next spring we can check for viability of offspring though genetically there will be a high probability of miscarriage.
Odd never had to answer that one before...
That's a nice, reasonable response considering the nature of the original line of inquiry. Some DMs would have just ran screaming for the hills, and not without some justification.