I'v never had Parakeets & D. Doves, in the same cage before, but have had RN. Doves, Parakeets, C. Quail, Cockatiels, Helmet Pigeons & a English Angora Rabbit all in the same flight before &...Parakeets ruled the roost.
If you have very tame keets or are keeping 4+ D. Doves per keet, go for it, it's worth a try, just make sure the cage is plenty big & that you have more then one feeding & watering bowls set up (& atleast 2 nests). I would have another cage on stand by just in case. Even though Cockatiel are bigger then Parakeet they tend to be tamer.
Try to get handfed &/or young keets. The younger & tamer the better the chances of it working out (english budgies sell better & for more & are said to be tamer) I'd sit by the cage for an hour or 2 after adding the new keets, so you can step in if it dosen't work out before the Doves get hurt. Also make sure they are not growing in new feathers when you add in the new birds, last thing any of us want to see is a blood feather get bit/pulled out...or worse.
Edit to add:
They do eat the same seed, although the Doves do enjoy split peas & black oil sunflower seeds as well, but they can be healthy & happy eating the same food.
~ Della ~