Oh you really need to pick up some bridal magazines. This day after brunch is a trend that was just getting started when I got married 5 and a half yrs ago. I can imagine its only grown since. And for those who do it it is frequently considered an extension of the wedding reception. Some couples even invite everybody who's coming to the reception. IMO since the Bride and Groom are attending the brunch the celebration continues until they have left for their honeymoon.
As for the shower, seeing as how it is still overwhelmingly a women event, I can't imagine him incurring any costs or needing to attend. If he can't spend 2 days in a row with his GF's family than they have issues they need to work out.
It's not a new trend. Every out-of-town wedding I've been invited to has included a breakfast paid for by the bride and groom (or their parents). It would be weird to expect people to attend breakfast together, as a group, at a certain time, and not pick up the tab.
If you want the guest to pay for their own breakfast, don't hold a group breakfast - let them get up and do as they please.