We've done this flight a few times from manchester. We have just been allocated seats when we got there - never thought to ask if you could prebook!
Plane - fine, nice staff, IMO more space than BA.
Food - well this is a bit hit and miss. Once it was fabulous, a full meal and desert, and once when there was turbulance we only got a packet of crisps or biscuits. In the morning you generally get hot drinks and croissants which really get you in a French mood! Bear in mind the flight time is only about an hour, so you tend to be stuffing the meal in before they take your tray back off to land.
Kids pack - very sore point with us, we have never received one yet, they have a limited amount to give out and if you are more than half way back along the plane you seem to miss out. Last time they gave the packs to the 2 kids in the seats in front of us and then said my kids couldn't have any as they had run out! I was very unimpressed.
Overall though I like them for a short trip. The only problem we had with them is that check in at Paris is appalling. We queued for 2 hours last time, panic increasing by the minute as it got to 10 mins before our flight time. They called our flight to the front of the queue (they were trying to board 10 flights through one set of desks) threw our bags on the belt, checked in and were then told we were on stand by! We tried arguing our case, but they were putting couples on and family groups were practically being ignored until it was too late. Then they said they were looking for 'volunteers' to step down as they had over booked. At this point it wasn't really a case of volunteering as the flight was leaving. The response was typical French shrugs and walking away.
However then the manager appeared and things started to improve. We were given phone cards, drinks vouchers and promised a seat on the next plane out (2 hours later) we were also told we would get 150 euros compensation. Not too bad we thought - although we were brassed off we had had to leave the park early - then out they came with 150 euros each! (we could also have chosen 1200 euros of flights if we wanted) So we ended up 600 euros better off for a 2 hour delay ...... not such a terrible thing after all then.....
Sorry if I've wittered on - but you did ask