...Charlotte was aware of all of the 'what ifs', she looked at them and for her the 'what ifs' were worth the risk more than what she faced as a spinster in her particualar situation. Also, as far as kids and if Mr. Collins died, the WHAT JANE AUSTEN ATE AND CHARLES DICKENS KNEW states this:

...in a society where power, money, and prestige were still often tied to the possesion of great estates and a name, an ecomomic transaction is really what it was (marriage). A husband often had to have a rich wife in order to keep up the ancestral family name in style. And since her fortune by law became her husband's property at marriage, the bride's family had to worry about making sure she and her children had something to live on if her husband died or were a wastrel. Women had a right of dower---or the income from approximately one third of their husbands' land---when their husbands died, but this was all but abolished by the Dower Act of 1833. Typically, then, the brides family would have their lawyers negotiate with the husband's lawyers to get the husband to agree to guarantee her "pin money," which was a small personal annual allowance, while he lived, a "jointure," a hefty chunk of property or money to support her after he died, and "portions" of money for their children. All this would be written up into a "marriage settlement" by the lawyers before anyone walked down the aisle. Even before the 1830 law these things were evidently being practiced because we hear of these terms in some of JA's novels. I guess this law made them a legal requirement.

I would assume that the right of dower was something that Sir Lucas took care of before he handed his daughter off to Mr. Collins. I'm not sure what this meant for Charlotte, particularly, since at the time, Mr. Collins had not yet inherited Longborne and was not in possesion of any land. However, "A contempory courtship etiquette manual says very straightforwardly that once you propose, 'your course of action is to acquaint the parents or guardians of the lady with your intentiions, at the same time stating your circumstance and what settlement you would make upon your future wife; and, on their side, they must state what will be her fortune as near as they can estimate to the best of their knowledge at the time you make the enquiry.' If Mr. Collins had nothing much to offer, under the circumstances, then the family and Charlotte would know this and just accept the 'what ifs' hoping it was something that would not have to be faced. If so, she would have rolled the dice and lost and have had basically the same options she had to begin with: moving in with a member of her family, etc.