Coast Guard is hiring now and offering bonuses. My father retired as an STSC in the Navy and he wanted to lateral to the Coast Guard once he saw where I was being stationed. Coast Guard has 2500 vacancies. $2000 just to enlist. 10-40k depending on which rate you go. Straight to A school for EM, MK, ET, OS, FS, BM. A school wait for aviators is 2-3months. I deployed with navy and would not recommend. The quality of life is nowhere near that of the Coast Guard.
I understand that your son is DEP with Navy, but if he hasn't looked at Coast Guard, I'd recommend he take a look. If he is going to have to wait, he had options.