T.S.
Are you having a scheduled C-section (hence, so sure about the delivery date?). IF not, you and your husband need to keep in mind that March 21 is your "working due date" and your baby could come approximately 2 weeks early or 2 weeks late. My first child came 15 days earlier than her predicted due date, just as an example.
I know that the 30th birthday can be a big deal, but so is having a child. You don't want your husband to partying the night away if and when you go into labor. This is just one example of how you and your husband are going to have to be flexible and put your child first. I like the plan of having a party or gathering in early March or you can have a big bash about 4 weeks after you have the baby and it can be combo B-day party for your husband and "meet the baby". You will not want to do much for the first 4 weeks, I promise you!
Or, you can tentatively plan to go out to dinner on the day and really enjoy the last few opportunities you have to go out as a couple without having to arrange for a babysitter..