sinces hes a pk you will need to breed the siblings together or a daughter to the father if you use your VT or delta.
If i was you I'd breed your blue girl, you will probably get VT and deltas with thick blue scales thanks to the dragon influence, if you breed a daughter back to father you will not only get his tailtype back (Plakat but probably deltas and SD, maybe HM if your lucky) but you may get some dragons aswell since the daughter will be have dragon influence.
your other female sounds like she could be cellophane, although she would give you better finnage in F2 it will probably take longer to get dragon back...
Although this is just me guessing. I dont know for sure what youll get.