To answer your question first: I ran a 3-way shop that was dine 25%, deliver 40%, and take-out 35% at our peak.
My question goes this way: why are you considering adding delivery? I am assuming to increase revenues. Bodegahwy asks very good questions along those lines. Then Thin2win throws in some additional costs considerations. Delivery can add gross sales to the top line, and even profits through to the bottom line. But, will you sacrifice your current brand identity to do so?
Delivery shops are generally considered lower position businesses than dine-in shops. I say generally,m because I know there are folks here that do a hopping good business with great market reputation, with DELCO shops.
If I could have removed delivery, I would have in heartbeat, because the overall profitability of a delivered pizza is lower when we already had everything set up for dine in. It limited our menu, increased our labor costs, and made staffing a chaotic mess in our small market. Since you are likely looking to increase revenues and profitability, is it possible to generate more dine in traffic? Dine in tables are generally higher ticket averages per 4 people, have upsell opportunities for beer, apps, desserts . . . allows menu variety with weekly specials, fresher food, immediate service dishes are more possible (like decent alfredo), more chances to develop face to face relationship/loyalty with customers. Yeah, it takes more staff training and time management of orders to do well and excel, but it is so worth it.
Just my thoughts.