To render with deferred load, change your bundle setup like so:
var client = Bundle.JavaScript()
.Add("~/scripts/jquery-1.7.1.min.js")
.Add("~/scripts/jquery-ui-1.8.17.min.js")
.WithDeferredLoad()
.Render("~/scripts/combined.js");
Web workers seem like overkill for something as trivial as script loading IMO.