Please check the sentences for grammar mistakes if any

Do these things matter to take final decision?

Does your noble cause end here

Let their heart sparkles with pride

Let your heart speak to them

I guess poetic license covers everything but number agreement.

I think your last two lines are subjunctive, and we would say, "Let their heart(s) sparkle with pride / Let your heart(s) speak to them  (Declarative is, of course, "Their heart sparkles / Their hearts sparkle".)

Edit.  Please allow me to suspend judgement on that last statement.  I just realized the lines are imperative, and I'm not sure what you call "sparkle," but it surely doesn't need to agree with "heart."

Sorry, Cg,  Mr. M. just saved my bacon.  The lines are imperative and the "sparkle" and "speak" are infinitives.  Have you tried the Search function  -  upper right-hand corner?  Google subjunctive works pretty well.

Best wishes,  - A.