I crossed Greenland back in 2009 and may have some advises for you. Based on the distance (2500 km) I assume you will be starting in south near Narsaq. If so you will have bad winds until you get to Dye2. From there you will normally get good winds from SE. (Please note that even though the distance from start to Dye2 is only about 1/6 of the trip, it will most likely take as much time as the rest of the distance. If you want nice winds and kiting every day you should consider starting close to Dye2 and head north to Quaanaaq.)
Which kite to bring is a matter of taste and experience. Personally I would bring the following: A large kite (14 m2) on handles with 60 m lines (pulls like a train), a pretty large depower foil kite (about 12 m2 Frenzy or similar) or a 9 m2 kite on handles, a small depower foil (access or similar - about 7 m2). You may consider bringing a 6-8 m2 parawing (skisail) as well for the howling days.Also, bring some line extensions so you can extend your lines to 40-50 m.
Forget about inflatebals. They are too heavy and lacks all of the abilities you want from an expedition kite. (I use C Switchblades for play but not for long trips). Flysurfers are good, especially if you are kiting in different terrain where wind varies. The huge wind range is nice, but IMO you don't need that in the flat terrain on Greenland. (I have a FS Speed 15 dlx. and use it a lot, but wouldn't bring in to Greenland.)
You should also have in mind that you will be spending a lot of hours behind the kite. Kites with handles are more relaxing to ride for long distances than kite with bars. They are also more effective pr m2 and cheaper. Btw, you will find the wind completely gust-free.
Since the dominant wind direction is SE and you are going N, the light wind machine on handles may be a low AR kite. You can then park it in the window and relax and enjoy the ride. A high AR kite may require some more active flying. We used a low AR kite as the light wind machine.
Since the time consuming f***-ups normally occurs when landing/launching the kite, you may consider taking fewer and longer breaks than the "normal" 10 min every hour. We did 3 h kiting and 30 min breaks.
I wouldn't plan on walking when there is no wind. Your sledge will be heavy (about 80 kg if you pack light). The distance you walk in one day can be covered kiting in 20 min the next. Relax and read a book when there is no wind. Also, learn how to kite in very light winds
Training on water will probably not be very relevant. You should practice as much as possible on snow with the kites you plan to use with a heavy sledge. Everyone makes mistakes. If you do them while training you learn from then and know how to avoid or handle them later on Greenland when nobody can help you. Therefore, realistic training is important. The heavy sledge takes some time to get used to and your upwind abilities will suck
Good luck. The trip is fantastic!
EDIT: About the sledges: Most teams use Paris Company Expedition Sled and mount two as catamarans. (like on the picture posted by vindman). They don't flip if mounted like that and are well tested. If you google it you will find they sell for USD 29