I'm not an ADCOM, but... It sounds like you are going to spread 30 credits over 2 years, so 7-8 credits a semester. That seems low unless you're working near full-time. Now, if you also put in 1000+ hours of ECs that might make up for the low credit hours, however, it could also come across as box-checking if you wait till the last year - although you would have substantially more hours than most.
Ultimately, you should focus on keeping a high GPA and find what works best for you. As long as you have a reason for a lighter schedule, you should eb fine in explaining it.