I would not add whole nuts or rice if you get alot of bowel obstructions. Big no no.
At least for me, rice hasn't been a problem, especially white rice. Just be sure it's thoroughly cooked. When I was recovering from my 3 bowel resections, about
the only thing I could eat was overcooked watery rice (what the Chinese call "congee").
Whole nuts can certainly be problematic if you're obstructing. Ditto for most high-fiber foods. Things that irritate the intestine (caffeine, the lactose in milk, alcohol, hot spices) are disastrous for me.
There are quite a few grains that do not contain gluten. If you like cooked cereal, gluten-free options include Cream of Rice, corn meal and steel-cut oats. In health food stores, look for quinoa.
However, I'm not totally convinced that gluten-free is of great benefit to most Crohnies. If you are sensitive to gluten, then definitely cut it out. People who have Celiac disease must eat gluten-free, but for Crohn's I've never really heard that gluten-free makes a difference. Nevertheless, feel free to experiment and see what works for you.