OLCI, one little question.

Hi guys, we are travelling to MCO on VS27 in Nov and we have already pre booked our seats but to be honest I'm not 100% thrilled with them. We have never done OLCI before and I was wondering if you can change your seats when you check in as I kinda have my eye on seats in rows 21, 22, 23 which were not avaliable to pre book. Are those seats reserved for a special reason as they are not bulk head seats. Any help would be really appricated. [y]