Overwhelmed with a few beginner questions

I want to purchase a projector most likely used. I have read a few things about lamp life and such. I am going to be using it outside during the summer months for movie parties for the kids. So it will be used about 4-6 hours a week over 6-8 months. I don't think purchasing a used projector for this is a bad idea as long as there are a few thousand hours left in the bulb.

My other questions are regarding if I need HD capabilities or not? I don't currently have a blue ray player and have mostly DVDs. My kids also still have VHS tapes they like to watch. They may also like to play the wii on it. I also plan to use a 100 inch BOC screen. I hear that I need at least 2000 lumens, is that true? Should I just make sure it has the three RCA jacks? What resolution should I look at?

Yes money is an issue but I am willing to spend up to $500 or $600. I have 9 kids and my house is too small to accommodate everyone's friends in the house but thought that having some movies outside would allow them to have friends over for an activity.

Sorry if this is covered elsewhere. I have just been reading all I can yet it just raises more questions. I just don't want to pull the trigger on something I will be unhappy with or better yet something my wife will be unhappy with.

I thought about that with the VHS. I will be showing the movies at dusk and after dark. I am going to put the screen so that you would be facing west as the sun went down. So I suppose that the screen would be somewhat shielded. We have a large playhouse that I can mount it on.

Thanks for the input.

I understand that this site is dedicated to quality video entertainment experiences. I debated about posting cause I know there are levels of any hobby. Beginners want to get in at the low to medium levels. And people who are deep into it sometimes give advice to stay out of the lowest levels. I do the same thing in the hobbies that I am deeply involved in. I just want to make sure I am not getting in to low as that sometimes turns people off to really great hobbies that if they would have just spent a couple hundred more they would have found enjoyment.