At any restaurant in Disney World it is important to include everyone in the reservation because of fire code regulations so you can start by looking for a reservation for 5. If nothing shows up, try for 6 since in most cases a family of 5 will be seated at a 6 top table. You could also try looking for smaller reservations (e.g. 2 and 3 or 2 and 4), but then you are booking smaller sized tables. When you check in at the podium you can ask to be seated together and in most cases it will be possible, but you may have to wait longer or if the restaurant is very busy you might be seated at 2 separate tables near each other or on opposite sides of the room. If you opt for 2 smaller separate reservations they will need to be made under the names of 2 different people.
However, there are some caveats at these 2 restaurants to consider.
CRT is a fully prepaid reservation when paying out of pocket so in this case it is better to book for 5 so you aren't paying for an extra person. It is also a relatively small venue so if you make 2 reservations it may take longer to be seated together or you might end up at 2 tables.
BOG: If you are booking breakfast or lunch, both are counter service where you seat yourself so if you get 2 reservations (close together or within a few minutes of each other) you will be able to sit together.
At dinner BOG is table service, but you have a better chance of being seated together even if you have 2 reservations because the venue has a large seating capacity. Not all of the tables or rooms are used at dinner because capacity is determined by the kitchen staff's ability to prepare and plate meals in a timely fashion. However, it is the one restaurant that frequently will not check in parties more than 5 minutes before their reservation time so the two reservations would have to be very close together in time.
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