On either dining plan you can use your meal credits anytime you want. Meaning, if you use up all of your CS credits on your first day on the basic DP, you won't haven any left for the rest of your stay. That is completely allowable on the plan.
Also on either plan your credits expire at midnight on the day you check out, if you haven't used them by then they expire. No refunds, no transfers no banking; use 'em or lose 'em.
The credits are pooled in your account. Meaning if you have 4 people staying 3 nights you'll get 12 snack credits. Let's say Disney Dad uses 6 credits, allowable on the plan; the family may have issues, but the plan will allow him to charge those credits.