Since you already have two people on your reservation, my understanding is that you won't get upgraded as an MVP (unless your wife is MVPG). That simplifies the situation.
With the possibly of an upgrade no longer a consideration, your dilemma is whether to purchase another coach seat for your daughter, or for yourself as a COS.
Wife has no status, so I guess no upgrade is possible? Disappointing but you are right it makes the decision easier.