Can't help you with the hotel but have just 'googled' the airline and it doesn't look promising according to the following website and a few others I've looked at. Hope someone else can give you more up-to-date and encouraging news.
http://forum.tunisia.com/recommendations/1471-karthago-airlines-2.htm

Thanks for the warning Aslemma, I've just read a few reviews , I've justed checked and the holiday is available flying with Thomsons for an extra £40 each

I think that might just be £40 well spent.

I stayed here with my family in May / June 2008 - we had a really good time. The party was my parents, hubby and me, and the children aged 12 yrs, 3yrs and the baby 8 months. There weren't many British guests in the hotel then but it didn't matter. We booked flights and hotel independently and got a very good deal - it was great value for money. The complex is large and right on the beach, good food (caters for European guests) - don't expect typical British food. As for Karthago, I flew with them in 2007 and it wasn't great, given a choice I wouldn't pick them but if there was no other option I would go with them but take my own food! After all it's not a long flight.