Thanking family for financial support

While we are paying for everything for the ‘day of’ our small destination wedding, my Father and wealthy Aunt/Uncle gave us sufficient money to cover accommodations (houses, which are also our venue) for nearly all our guests. The contributions were equivalent but it was a bigger financial sacrifice for my Father. We are so grateful for their help as our dream venue wouldn’t have been possible without them. We’d like to thank them, but not sure what would be appropriate? I also don’t want to embarass my Mother or FILs who were not able to contribute financially. How should we word the thank you? Should it be public or in private? Should we thank them at the Rehersal? Reception?