I think it was also SJS that had multi hole cranks that were shorter.
Edit: 110/145
https://www.sjscycles.co.uk/cranks/t...s-104/?geoc=US
Da Vinci also does but they are expensive. Theirs are 130/150/170 or 120/140/160
Components - da Vinci Designs
125 mm for a 3.5-5 yo is a hard ask, they really can’t reach nor do they have stand over to the ground. But a kidback puts them really high. Crank shorteners on the back of a tandem have a big Q factor too.