The groom's parents are contributing a considerable amount of money toward our wedding (though nowhere near half). Is it proper to include his parents on the wedding invitations, i.e., "Mr. and Mrs. John Doe and Mr. and Mrs. Tom Smith would like you to share in the marriage of their children..."?
Here's the funny thing about people's names on the invitations -- everyone thinks it signifies who's paying for the wedding, and a lot of the time, the parents listed are paying -- but the larger meaning is that they are hosting the reception. "Hosting" is a word with flexible meaning. Parents can be official hosts -- they planned the party, they invited the guests, they paid -- or honorary hosts. Maybe the couple paid for their own wedding, but still want to honor the bride's parents and the groom's parents on the invitation. Technically, all four parents can be listed on an invitation without putting a penny toward the wedding. (This usually isn't the case, of course.)
It's more diplomatic to list all four parents, even if the bride's parents are putting more money into the wedding. If nothing else, it's a wonderful way to reach out to your new in-laws. And these days the bride's parents aren't really giving her away anymore -- why should the groom's parents get shafted on the invites?
Whatever your take on that, since his parents are contributing and you have raised this subject, you should include their names. You can either do it the way you suggested -- with both sets of parents listed on top -- or insert their names after the groom's name, with the line "son of" in between.
Wedding Invitations + Wedding Stationery