As long as the restaurant is okay with your splitting up the charges, it should be okay with Rewards Network. However, you should check both the PC Dining and Southwest Dining sites as, on rare occasion, a restaurant will participate in some programs (partners), but not others.
Relatedly, if you run across a listing for a joint that has a once-per-month earning restriction, that's per partner so a split check between partners there should work okay, too. What you cannot do at those places is split the check on the same card (for additional "elite" requalification credits)! If you did, the one that went through is all you'd be entitled to, period.