When DS2 was just 2, he had a major operation to remove a section of bowel and was fitted with a colostomy to allow to operation site to recover. Not easy with a very active and mischievous toddler. No district nurse or health visitor came to see us. Two or three times he fell flat on his face, the stoma prolapsed and I had to take him to hospital to have it put back under anaesthetic. Eventually, after two months, they decided enough was enough and closed it. There were one or two setbacks but he was a robust child and is now a 48-year-old dad, still taking part in running, cycling and hockey.
So your grandson should be fine as he is old enough to be careful and not let the thing prolapse. He might not be able to do all the activities that he peers take part in, but perhaps by the time he is a teenager, he will be able to live a more normal life. Good luck to him.