My one year old is dairy free, soya free and tomato free. He doesn't do well with fish either.
We use oatly milk alternative, it's in the long life milks section. They also do a cream. I use this to substitute any recipes that use milk. You could also try almond milk, koko, soya or rice milk.
Cheese - violife is by far the best DD cheese, they do a block and a creamy one that is like Philadelphia. It doesn't melt well though.
Butter - we use vitalite, pure spread is good too. Use this in any baking etc. You can also use a stork block.
Most of the 'just roll' pastries and crossings are dairy free. You get them in the fridge in the supermarket.
Desserts - alpro soya yoghurt, birds custard powder and make it with a df milk. Xotic and wot no diary are available from Holland and Barrett. Coyo too but these are expensive. Fruit sorbet instead of ice cream.
Dairy free is easy when you get in the swing it, I find the tomato free bit far more difficult!