I have been doing wedding/bar mitzvah invitations for myself b”h, and family and friends for years. I always use excel for the master lists and merge with word for the labels and envelopes. I keep a master copy on excel and suggest that everyone keep a master list and make changes to that list as they get invitations from others. Keep that list current with changes of address, etc. Make a copy of that list for your current simcha and use that for the data base and name that your current child’s name. Use that one for sorting, inserting replies, etc.
When making the data base, use separate columns for title, male name, female name, last name, address, city, state, zipcode. It will be much easier to sort and make seating cards later. Even if you split the Title it will make it easier for the seating labels later. Even just for the purpose of finding someone a ride to the simcha, having the zipcode in a separate column is very helpful.
OK, that was my two cents worth of experience. Oh one more thing. If you are going to be putting the envelopes through the printer, MAKE SURE YOU DON’T BUY fancy large envelopes that will give you a hard time, in addition, you will want to have a smooth texture and not the lined ones the smears the ink.