Next time you are shopping pick up a bag of Channa in the asian bit ( they are split dry chickpeas) these make the best dahll imo as they keep some shape to them - so a bit of bite. You need to soak them - i just put them in some water in the morning and use at night. I potato mash at the end and you get a great texture.
I have read that a few chopped tomatoes can replace the tamarind flavour - i normally add a small handfull of cherry tomatoes.
see, i find the sains one dry too, the lentils are all bitey! What I would do is, cook the dhal separately, then heat some oil, add whole spices, fresh diced tomatoes, then mix that with the pureed dhal, and add ground spices, then cook through.
I've never used tinned lentils apart from chickpeas. I use dried, soak overnight, or for a few hours when I remember and cook in a pressure cooker.
shop bought are dry because the lentils aren't cooked for long enough or with enough water. I make gujarati style, and I actually blend mine. I will dig out the recipe if you want it, but I don't think it has tomatoes in it.
For the kids? I have bought a lentil dahl from Sainsbury's before which they ate, but then I tried to make my own and it seemed a bit dry. Needless to say they turned their noses up at it. I think they'd go for something in whizzed tomatoes - any recipes or shall i just make something up and hope for the best?