Just to let you know that I've just tried this myself for a delivery tonight. As long as you order £30 worth of food first for the 50% discount you can then also add the 2 for Tuesday onto the order, defo. So anyone needing 4 pizza's or if you're just being greedy you can order these to benefit from both.
Also, although it says you cannot use the offer with ice cream, you can with the other desserts (waffles/cookies etc) as just done so.
Hope this helps some peeps.