תרגום - ספרדית-לטינית - ¡El amor de madre es todo!

omne--> omnia

The meaning of the Spanish sentence is like "The love of a mother is all (all=the most important and needed thing)" I suppose.

Should it be "omnia" the same?

Yes, Alex. It can't be "omne", because the adjective requires some noun in neutral gender.

Compare, please:
Tu mihi omnia es. = You are/mean everything to me.

Sorry, I didn't know it.

No problem.

Just to be clear:
omnis, omne = every
omnia= everything, all