Don't try to use labels and print them. They should be hand written in pen and ink.

Use the format that comes with the program for printing the invitations.

Make arrangements to rent chairs for the ceremony. They don't cost much and it is TACKY to ask people to bring their own chairs!

After reading this question I begin to wonder if you are going to have possum on the menu at the reception.
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Unless you take it to the printers and they emboss/use raised ink then you cann't print in white so you will have to use lables.

For the wording I would do something simple like:
"Guests name"
Together with their families
Bride and Groom
Request the pleasure of your company at the celebration of their marriage
on whatever date (written with words, not numbers)
at whatever church
Dinner and dancing to follow
at wherever the reception is.

You might like to include the lawn chair information on a seperate card. You could also put the reception information on there and the dress code if you have one.

For your printer you need to set up the page in Word (if that is what you are using to write up the invites)
Go to file, page setup.
Change the page size, orientation and margins to suit the paper you are printing on. it usually shows a preview box so you know whether it worked.
Go back to file, print setup, change the settings for your printer to be the same as the paper.
Do a few trial prints on scrap paper cut to the same size as your invites to see whether it worked.

Good luck!
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For the envelopes, its best to handwrite the names and addresses. Its the traditional way, and it adds a personal touch. Use a white or silver gel pen and it will look great. (Labels look impersonal and lazy, and also white labels on a dark envelope is not pleasing to the eye.)

You can do this. Good luck!

**I dont think you should ask them to bring their own seating, but thats all I will say about that.
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for the invitation wording you can look at the link below for ideas:

http://www.ltmparty.com/wedding/invitations/wedding_invitation_wording1.aspx

wedding invitation- some guidelines…
http://www.foreverwed.com/Invitations/wordingforweddinginvitations.htm

here is my idea for you invitation:

Please join in the marriage celebration of
Michael & Melanie (along with their children Chris and Abby)
On
September 6, 2008 at 3pm
Mission Park, Mission, ON
(address)

Reception to follow at 5pm,
Mission Community Centre
(include address..)

*As the wedding ceremony is outdoors please be dressed for the weather and bring your own lawn chair or blanket to it on

congratulations and best wishes!
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