Totally agree, they are fine if that is all you have - better than nothing, but don't make a habit of it.
Think of waxworms like candy, or bon-bons, or some other fatty food you just can't resist. There is the possibility of addiction, like giving a child candy all the time and then they refuse to eat a proper dinner. We've broken a few addictions here, a gecko - like a toddler- will eat what is offered before starving, but it is something to be avoided if possible.
You may notice a change in their poo due to the high fat content of wax worms, just a heads up.
As a rule, I would go no more than 3 waxes a month as a treat, but in special situations, like yours or an underweight, short term wax worm feedings is no problem. I would say an adult 2-3 worms every 3 days and you can stretch that out a bit too if your geckos are well tailed. Don't be surprised if that first feeding of your normal meal doesn't go as well, but don't worry a week or two is more likely going to make them stubborn than completely addicted. 
And it happens to the best of us. We just had a cricket shortage tonight and one of my girls is looking a little forlorn that she could only find one cricket in her shaker. Thankfully, it is only a half hour drive tomorrow and she'll get the rest she was due. Here's hoping for speedy delivery on your end!
