Whoa...wait a minute...are you sure this is a good plan? Have you looked at your budget? Have you booked your locations and considered how many people your favorite venue can accommodate comfortably? Last but not least, have you calculated your "per-person" costs such as catering, seating, place settings, etc?
Friends of your parents that you haven't seen in years, cousins in another state that you were never really close to in the first place, and co-workers you feel you should invite (just to avoid being rude) shouldn't take up prime real-estate at the biggest event of your lives. Every guest multiplies your cost and divides your time and attention. So let's work through this process together.
First, consider how many people you want to be there overall. We should start with immediate family & closest friends, then move out to other family & friends that are important in your lives. (Don't forget to count single adults as 2 to allow for a guest/date.) You can safely continue moving out until you reach approximately 120% of your desired guest count because not everyone will be able to attend.
This process may sound calloused, but as you move farther into your planning, you'll be very glad you controlled your guest list instead of letting it control you. It's not about being "cheap". It's about directing your funds to what matters most to you and makes the day special for those who truly share in your lives.
Don't feel bad about those who are left out. We all have people we like & want to be nice to, but sharing in your life-long bond as a couple is for your inner-most circle. Besides, you are likely letting some of those "would-be guests" off the hook. How many of us have attended weddings out of obligation just because we were invited? Then spend the entire time contemplating other ways we could've spent our weekend??
Have fun with your planning! Getting past the guest list is a serious milestone. Once you have this piece behind you, you'll be surprised how easily some of the next steps can fall into place.