How long can I keep an uncooked egg casserole in the fridge?

Thanks Nancy and Susan. I think I'll do what you both suggest and prepare as much of it in advance as possible but not assemble it until the night before (yes, with a glass of wine!) at the party house. This way I can add the eggs when I get there, not worry about it all drying out, and have fresh (as opposed to reheated) casseroles. Thanks for your suggestions!

Oh my gosh..yes totally safe in a cooler for 2.5 hours. Especially with ice. The coolers are made to keep the cold items cold for hours. Add ice to the mix and Bob's your uncle. Here's my only thought. Is there anyway you can assemble it on Saturday morning or even when you get there? I'm not worried about food safety, but your casserole may be a little drier than it should be. You could even prep the different ingredients (chop onions and brown sausage for example), package it and assemble Saturday night while sipping a glass of wine.

Kathy - I'm an experienced amateur but not an expert on food safety. Still, I worry that ice alone in a cooler is enough to keep the mixed uncooked casserole at safe (about 40F or 4C) temp for several hours.

Options:
1) go back to original plan, mix & cook Friday, take in cooler with ice Saturday, refrigerate overnight, serve Sunday (chilled, room temp or re-warmed)
2) mix & freeze the custard on Friday (without a crust or bread), take frozen in cooler with ice on Saturday, refrigerate on arrival, add bread to soak for French toast or the like, bake Sunday morning.
3) take refrigerated unmixed ingredients in cooler with ice, mix at location, let sit in fridge overnight, bake Sunday morning (less chance of contamination with eggs in shell, sealed milk etc)
4) take advice from someone who IS an expert in food safety (here at food52, a home economist at your local electricity company or county extension, registered dietician at city hall, etc.)

This is beginning to sound worrisome. Is there another easier dish you could contribute...good luck, whatever you do.

A reliable site that I often consult on durations for both fresh & packaged food says 2-4 days refrigerated for open raw eggs.
http://www.stilltasty.com/fooditems/index/17145
since yours will be open approx 1.5 to 2 days (depending on when Friday you mix your casserole), it sounds like you're well within the safe range. also, it will taste better if cooked fresh.
Only thing I'm worried about in this scenario is your Saturday travelling.
Will you be able to maintain temps similar to refrigerator for all your travel time...if not, maybe cook ahead.