Looks like a great hunt to me! I'm thinking the larger buckle dates to the mid-late 1700's. The smaller buckle looks older to me. Congrats. Gotta love the old stuff...especially when you can pull an intact shoe buckle out of the ground!
Agreed with Agmonkey. Two of the buttons look like large coat buttons popular in the latter part of the 18th century. I've found quite a few shoe and knee buckle parts, but only one with an intact chape like your.