I've cobbled together accommodations for my 4- and 6-year-olds while I wait for the caboose and running boards to be available. We had a Yepp seat, so the 4-yo rides in that. It's a little on the small side, but workable for now. The other items are:

• Xtracycle Mini Magic Carpet https://www.xtracycle.com/product/mini-magiccarpet/
• BMX pegs (someone else found better folding ones on Amazon)
• Seatpost handlebar https://amzn.to/38Iatdv

I heated up the handlebar with a torch to adjust the angle, since it interfered with the seat as delivered.