If DS1 (now 10) wanted to try it out, I'd let him, no problem.
If DS2 (now 8) did, I'd say no. We already have to provide him with a dairy-free, wheat-free, gluten-free, colouring, sweeteners and preservative-free diet. Meat is essential for him, IMO.
So, DS1 as a 5 year-old - yes.
DS2 as a 5-year old - no.