May one order children’s shoes on Chol Hamoed? They will be needed for a Simcha soon after Yom Tov, and will likely not arrive on time if ordered after Yom Tov.
One is not to plan activities of buying and selling for Chol Hamoed.
When there is a need of דבר האבד (that the thing will be lost if not done during the Moed) one may buy on Chol Hamoed, provided it wasn’t planned for Chol Hamoed. The purchasing should not be done in public (which can be accomplished through placing an order from the home).
.ראה שו”ע או”ח סי’ תקלט סעיף ט ובאור הלכה ד”ה ומתר לקנות