Boy can I relate. We have 3 kids and bought a new pop-up 18 months ago!
Here is what I would suggest looking for:
1. New or used, buy a brand that has a dealer near your home who can service it, fix it, and answer questions.
2. Make sure you pick a pop-up that does not exceed your max towing weight on your vehicle (especially with luggage, extra people, bikes, etc).
3. Decide what size "box" you want (camper size under the roof). Little ones are 8 feet, some 10 footers, and some are 12 footers. Bigger means more room but heavier (see #2).
4. Consider a pop-up with a slide-out dinette to give you extra room inside on cold nights, rainy days, etc...Slide-outs add a little extra weight (we have one) but the extra room is worth it. With 3 kids, sometimes we need room to spread out.
5. Consider getting the shower/potty option if available. We did and are glad. My wife and daughter appreciate not having to go outside at night to go to the bathroom when they are in their jammies. I close it down during the day to give us extra interior room. We only camp at state parks, Fort Wilderness, etc but it sure is convenient not having to go out when it's cold, wet, etc.!
6. Some folks like to have the fridge directly across from the door so that you can stock the fridge before a trip without having to put up the roof. Ours is not in line but it's not a problem.
7. Some models have a big storage box across the front of the camper (ours does). We like it to throw hoses, lanterns, folding chairs, basketballs, etc in. You can NEVER have too much storage space in a pop-up.
8. Other options like A/C, heaters, ovens, microwaves, cable tv jacks, radio/cd, hot water heaters are up to you. (we have all those listed and like them).
9. Consider bed size (double/queen/king), how many kids you have, and how long you expect to keep the pop-up. A double might be okay if they are little, but if you have teenagers you will want a queen at least.
Get one and have fun. The first couple trips stay close to home, learn how to hook it up, pull it, back it in, and then do it all in reverse to take it home. We love our family time together. Our kids are now 8-13 (3 of them) and we camped 28 nights last year.
We will be at Fort Wilderness later this month for 8 nights. Sure is nice to pay for just a campsite, to have our kitchen/fridge with us, and to be able to take our bikes. I am SO looking forward to relaxing.
We have a 2005 Jayco 12 HW (12 foot box HighWall model) and are very happy with it. Check out their web site!
Good luck and see you 'round the Fort someday, maybe?
Bama ED