I live in Fluvanna and work very close to the courthouse and the county library, and I am originally from Albemarle. I can check the courthouse marriage records to see if a surety was posted, but I have found out some information online that you may not be aware of yet, and I checked a couple of sources at the county library.
The Library of Virginia in Richmond recently began putting online some of their collection of chancery causes (court cases to resolve disputes).
The link to the search page is here:http://www.lva.virginia.gov/chancery/
Go to the box for "surname" and enter "allegre". Find the case with the index number: 1825-006, William Payne, jr and wife vs. Administrator of James Alligre.
This case was brought by William Payne Jr in right of his wife, Maria (Allegre) Payne and petitioned the court to require the administrator of James's estate to divide his property for his heirs, who were all children under the age of 21, one of whom was Mary W. Allegre. The others were: Eliza P., Albert G., William R. and Maria C. (wife of William Payne). The administrator was William T. Allegre, brother of James. So, it seems likely that this is the correct Mary Allegre (I checked and ruled out another Mary Allegre from this area who married a John H. Wheeler, and was James's sister). James Allegre was married to Lucy Watson, who apparently died around the same time as James. At the time of his death James owned over 1000 acres. A book of Fluvanna marriage records at the library lists Robert T. Cross and Mary W. Allegre as being married at a Baptist Church by a Stephen Eastin, but lists no surety. Another book at the library lists one of the early members of the Beaver Dam Baptist Church as being Stephen Eastin, and that William T. Allegre was a trustee. That church is still active and is located very close to what was once the Allegre Tavern.
A later chancery cause (1843-002) brought by Betsy (Allegre) Davis, a daughter of Daniel Allegre and sister to James and William T. Allegre requests that a new person be named as trustee of her legacy from her father Daniel, as the two trustees named were James and William T, and that by this time in 1843, James was deceased and William had moved away to Missouri (where he appears by the 1850 census).
So, it appears that Mary W. Allegre was the daughter of James Allegre and Lucy Watson and James was the son of Daniel Allegre and Susannah Tisdale.
Also check the Library of Virginia website and search for land grants to the Allegre family. It appears that the various members of the Allegre family obtained over 3500 acres of land in Goochland, Albemarle and Fluvanna Counties. The land that Mary W. received from her father's estate specified that it was on "Mechump Creek" (Mechunk Creek); the Allegre Tavern was also along Mechunk Creek.
Link to the Library of Virginia land grant research page:http://lva1.hosted.exlibrisgroup.com/F/45GGEKPIQ1C45XYPYVDMN...
Good luck with further research and let me know if I can be of more help. Feel free to email me directly at mhineline at embarqmail.com.