Are there no dogs allowed on the beach? Why not take them with you on the beach, just harness them, use a long retractable leash and have them be part of your family? I would nto ever consider teethering Yorkie's for any length of time.
LIke others suggested , use a ex pen if you can't take them with you to places. Keep them in the RV, and make certain the Temp. is not HOT. Otherwise, if all else fails, maybe they can be boarded , or a family member can take them while you guys are away.
IMO, is that owning dogs you have to always do what is right and GOOD for them. Never settle for anything that could possibly endanger them, especially a little yorkie.