in a wedding 2 weeks before due date

So I am suppose to be the matron of honor in my sister's wedding two weeks before my due date. I am nervous to announce the pregnancy  to my sister for this reason. Her wedding is in another state from where my husband and I live so we would be traveling for the wedding. 1)Is it okay to travel so close to my due date? 
2) how do I tell my sister and her finance that my family is growing? 
3) do I decline to be in her wedding due to being very pregnant at the time of her wedding? 
Any advice would be appreciated!