Why can't he have some whey preworkout? And HOW in the world does dextrose put you in a catabolic state? Any carbs around your workout have the effect of limiting cortisol therefore staving off a catabolic effect. Much the same as protein but even more pronounced if consumed together.
As far as shakes bloating you I think people should speak for themselves. But I agree of course that the majority of protein and all nutrition should come from real solid food. There are places, however, where a shake is very effective and handy and some whey (which is just protein for God's sake) isn't gonna hurt the OP. You defenitely should not be replacing meals with it though
and dextrose and malto should only be used around the workout. And they should be used together. Dex by itself SUCKS. You need the mixture.