FWIW in my opinion you made a good decision. I enjoy having a large Hasselblad system with a complete array of lenses, and a plethora of backs, finders and various accessories. I agree with other posters that you are going to be going through a learning and familiarization period. The key to developing a good respect for Hasselblad and what it affords you is to give yourself time to become comfortable in using it, and that does take time. It will not happen overnight. A Nikon SLR and a Hasselblad are completely different animals. The only thing that remains the same are photographic fundamentals. The equipment demands a totally different technique, more disciplined, more exacting. I think the use of a Hasselblad generally makes most users better photographers over time, similar to what large format users experience. It is exquisite equipment and a joy to use in my judgement. I hope you are pleased with your new gear after you receive it and that it meets all of your expectations. I would recommend a prism as well as others have pointed out, I use a PME III with Acute Matte grid and split and like the combo a lot. I would recommend a quick focus handle for your action shots with the children.
I think we would be interested to read any opinions you may have after you've run a few rolls. That may help others in the future whom are in a similar decision making process. The system will grow on you and you will probably be hungry for the next component before long. Enjoy.