DVD Backup questions

I am new to backing up my DVDs and was trying to put all of my East Bound & Down series on one DVD+R it is 4.7GB 120 min. All the files together are 5.24GB and is longer than 120 min. Can anyone give me some advice on how this works. I have kids at the house and it is hard to keep DVDs from getting destroyed and don't have enough cash flow to just go out and buy new ones. Most of our Disney movies are gone. I gotta do something before they are all gone. I got WinX DVD Author from here and is great. But running out of DVD+R and money.
They are in AVI format.

 

You can use this program : http://www.freemake.com/

Enter your avi files to DVD and it will convert and shrink to allow you you to put the files on one DVD.

 

Or use DVD+R Dual layer discs if your burner supports them.