Why oak? Isn't that more expensive than those Ramin dowels? Oak is probably more durable but heavy too. It's a pain to sort through all those dowels, but getting the straightest grain is best.
I have a couple grandsons at 8 and 10 and I find they are not too picky about their arrows and will shoot about anything.
I also check out the vendors at the shoots. Last summer I picked up 4 doz. Doug Fir shafts, 24" long, tapered both ends, for a buck a piece. They were 5/16", and I installed 75 gr. pts and made up arrows for plinking and 3-D. I only wished they were 29" for that price!
I also pick up used aluminum in the lighter spines and they work ok as well.