The NSW Health Department has a caffeine fact sheet that lists caffeine content of various things - it lists cocoa and chocolate as also having caffeine so not sure hot chocolate is a good tea replacement. Personally I think everything in moderation, DD has the occasional bit of chocolate which also has caffeine in it, so the odd sip of tea here and there I don't think is an issue. The caffeine content of tea depends on how strong the brew is and if is quite weak which when DD has it normally is as add lots of milk to cool it down content can be almost as low as decaffeinated tea/coffee.

What How much caffeine? Comments
Instant coffee 60-100 mg per cup The amount of caffeine depends on how much you put in the cup
Fresh coffee 80-350 mg per cup The amount of caffeine depends on:
the type of beans ('Robusta' contains more caffeine than 'Arabica')
the way the coffee is made
how strong the brew is

Decaffeinated coffee 2 - 4 mg per cup The amount of caffeine is usually marked on the packet
Tea 8 - 90 mg per cup Caffeine content depends on how strong the brew is
Cola drinks 35 mg per 250ml serve Cola drinks often contain a lot of sugar too
Cocoa and hot chocolate 10 - 70 mg per cup The amount of caffeine depends on strength of the brew and the other chemicals in the product
Chocolate bars 20 - 60 mg per 200 g bar Chocolate also contains a lot of sugar
Some prescription and over-the-counter medications 20 - 100 mg per dose Some medicines (cough, headache and slimming products) contain caffeine.