My daughter learned to ride on a Winkie english trike and then on to a 20" Raleigh Mountie, lugged frame, Brooks saddle, 20x1-3/8" wheels. We rode in the Philidelpia British bike weekend 2 years ago and she did 7 miles with the group without a hitch ( at 6 yrs old). Twice around the block was her longest ride until then. The boy was happy to bring up the rear in the Perry seat on the '35 Sunbeam tandem. She already know's how much easier it is to ride a "lightweight" than the Sting-Ray that is also in the garage. I have a NOS Raleigh "Space Rider" prepped for her when her leg's are ready, 24-1-3/8" , WW's and SA 3 speed. She does not even look at bikes when we are in the discount stores. I hope I have as much luck when she wants something that takes keys.
The only Aluminum frames in the garage are '36 Silver Kings (lugged)