If you are not sure you will have 10 or 11 people, make all of your reservations for the maximum number who might be dining. It is always easier to show up with fewer than try to add someone later who wasn't on the original reservation. Everyone who will be at the table (including infants and non-eaters) needs to be included.
AS far as the size of your group it is better to start with one reservation that includes everyone - so 11 and even 12 since sometimes the reservation system has problems with odd numbered groups. If you have smaller reservations (e.g. 5 and 6) the castmembers have no way of knowing you are one group. While you can ask to be seated together when you check in at the restaurant it is just a request and while castmembers will do their best there is no guarantee. You might be seated together or near each other, you might have to wait longer for two adjacent tables to be available at the same time or you could be seated at opposite sides of the room. If you have a single reservation for 11 the castmembers will know you'll need a larger table and while it might not be possible, you'll have a better chance of being accommodated.
