Sam, I would look at splitting your `formation` into separate groups,as to be a `formation ` you should keep relatively close together,maintaining similar speeds; there should also be a nominated leader,deputy leader, air2air nominated frequencies,and each group having a separate c/sign,and separate txpdr codes(only leader squawking,deputy/ies on stby). It is rather difficult to control what one may have as a `gaggle`,as you probably have people of different abilities,experience,mil/ex-mil,all civvy,and everyone wanting to be leader,or be a sheep. You then have to have PLANS B-X if things go adrift,lost `sheep` comms, fuel plans etc. Then you`ll have to consider if it`s all VMC/VFR,if there`s any IFR,and finally IFR/IMC. Also consider that fuel may be a problem in that the `hangers-on will use more than the leader.
It`s a big undertaking /reponsibility to be the leader,so work on `KISS`...If I can offer any advice/help,send a PM.. The flight plan will be the least of your worries,but ,all the best!!!!,Brian..