Why don't you suggest soaking feet in icy water befor the dance , num them with cold ?
Why not suhhest taking 3 pain killers, or a double Lidocane injection, should kill the feeling till the dance is over .
Suffer not now, suffer later.
Metatarsalgia is a chronic condition, you need use special orthotics in the show, no Dr. Sch...will help. Take this seriously, you may dance a few years, but you must walk on your feeor for the rest of your life.
Use flats, see a dr. get fitted orthotics, take antiflammatory medication as the swelling presses on a nerve causing pain !
Good luck, and do not wait for any cows to go anywhere :)