help starting my first d&d 3.5 adventure as GM

[drewdp]

So I haven't played d&d for about 9 years. I wanted to get into a rpg but couldn't find a group with openings and finally decided to run my own campaign with friends who have little/no experience in rpgs. Well, while assembling the group I got people saying no, so i asked more people. Then the first people came back saying yes, while the others I asked said yes, and here's my friend who's gonna play with us. Now I have a group of 7 people wanting to play in the same game.
A, any suggestions for or against running a group this big?
B, I'm trying to plan out a decent initial adventure for them so they can get the hang of the mechanics. I've been playing around with this (http://creaturecatalog.enworld.org/fiend_factory/elc/encounter_calculator.htm) encounter calculator, but was just wondering if anyone had a suggestion on what monsters to use?

My plan is this: They all meet up in a small village a mile or so from a main trade highway. The rumors they will hear are that a child has gone missing, a woodcutter saw a group of [insert enemy] near the caves in the foothills, and that a dragon was seen flying in the mountains.

The plan is that the group of kobold or w/e abducted the child and are keeping it in the caves, and the party must go and rescue it. I'm just wondering what would constitute a good enemy for them to fight? The plan was 3 encounters with the enemy, as well as a 4th encounter down a side passage with some type of animal, perhaps a (large) monstrous spider.

So should I be using kobold, goblins, w/e. The Ideal would be for each encounter to have 4-5 enemies. But if i have more than 10 total that indicates a band in which case there are non-combatants as well as a "boss" leader of 4th-6th lvl, which i'm not sure how to design, or if 7 lvl 1's would be ok handling.

[HammeredWharf]

I wouldn't trust encounter calculators. The CR system is notoriously broken and works even worse with large groups. Just look at the monsters' stats and evaluate how well they'd fare against your players. If you want to measure how well the party works, give them a small-ish encounter and introduce enemy reinforcements, if necessary.

A group size of seven shouldn't be a big problem. I'd avoid single-enemy fights, because the group will have a huge action economy advantage in them. For that reason, I'd rather use two or three medium spiders instead of a single large one.

[hemming]

So should I be using kobold, goblins, w/e. The Ideal would be for each encounter to have 4-5 enemies. But if i have more than 10 total that indicates a band in which case there are non-combatants as well as a "boss" leader of 4th-6th lvl, which i'm not sure how to design, or if 7 lvl 1's would be ok handling.

I would treat the guidelines here with a grain of salt - you don't have to put a higher leveled creature in

If you do want to throw some levels on a kobold you just treat kobold as the race and level it like you would any other character

I often use the NPC tables in the DMG (p113) to quickly add multiple levels and adjust for the monster type