Is it valid to suffice with the offer and include the acceptance from you in the marriage contract, or must you utter the offer yourself, given the significant embarrassment caused by difficulty in speaking?

One of the pillars of marriage is the صيغة (formula or expression) which includes the offer (ijab) and acceptance (qabul). The offer alone is not sufficient. For acceptance, saying "I accept" is enough. It is possible to avoid difficulty by appointing someone to articulate the acceptance on behalf of the husband, as deputyship in this matter is permissible and has been confirmed by the Prophet, peace and blessings be upon him.