Terminally Ill Mom's Dream Wedding

My (future) stepmom was diagnosed with terminal cancer in October. She and my dad have not married because they have 7 children between them so there hasn't been time or money. Her illness made it clear that there is no excuse for people who love eachother not to have the wedding they dream of. 
She and my dad are so selfless and I want them to have a really special wedding. Because my stepmom is going through treatment, she won't want a big wedding but having enough money to get her a beautiful dress and pay for a church by the sea will make her really happy.
The wedding is set for early January. Please help me make this a special day for them. Any help you can give would be hugely appreaciated.