It doesn’t really work here and certainly not in a short note on a postcard. The first meaning of consume is use up as in: That car consumes a lot of petrol. The use of the verb with food and drink is usually only used in a formal way as in: The police reported that the accused had already consumed 4 litres of beer.
It could be past as well, but then it would refer to a particular breakfast they had. In this case, as there are only present tenses to chose, it means an action which is quite usual:
‘At home we eat a big breakfast’
‘We never have breakfast after 9 am at home’
It implies a common action, performed with a regular timing - it could be on a daily or weekly basis.