You could opt for a PH or concierge level cabin to get a head start. If you go to PH or above, you are not obligated to use your butler but may find him of some value. Absent spending money to get an earlier booking time, you will have to be very flexible in your dining time and keep a look out for cancellations before and during your cruise.
We tend to opt for sharing for our specialty restaurants and over the past 12 or so dinners have only had 1 that I regret but that was down to the fact that 1 couple did not really fit in. You could try redirecting the conversation away from politics. Don’t shut the conversation down, but let them finish their thought and then tactfully change the subject. Talk about previous travels, their children, their jobs, their hobbies, etc.