First, congratulations father to be!
If you plan to use infant carriers (removable bucket in a cradle) for the first year-ish, don't buy a convertible yet. Car seats have expiration dates and most are good for 6 years from date of manufacture. No point in acquiring a seat not you won't use for a year and then getting 1 less year of use from it. Is the Patriot going to be your main family vehicle? My Jeep is the secondary family vehicle. It has worked well for almost every 1-day trip/excursion. We also have a minivan.
That said, I will warn you that infant carriers are longer than convertible seats even when reverse facing. I have a relatively short
Graco Snugride and it has to be placed in the center in order to fit as it squeezes between the front bucket seat backs. Putting the infant carrier directly behind either driver or passenger seat makes makes the front seat unusable. Since you have twins coming, you may want to skip infant carriers and go right to convertibles.
I have an Evenflo Titan and a Britax Marathon. I have two kids, older was 2.5y when second was born. Another one coming in June. My older used both of these seats in two different vehicles (wife's/mine). Once my younger moved out of the infant carrier, my older moved into 2 Britax Regents, one for each vehicle and my younger now uses the two convertibles. I love the Marathon, but it costs 4x the Titan. The Marathon will laster longer as harness slots are a lot higher and is easier to install in vehicles and use/adjust harness.
Budget? Costco Scenera is a great starter seat. It is similar to my Titan, but even less expensive. It is available at every Target/Walmart/Kmart/Sears/etc for under $50, as low as $35 on sale. A few colors, pink for girls and neutrals for both sexes. That should get most kids to the age of 2, maybe 3 and you can consider something like the Graco Nautilus at that time.
You should find a local Babies R Us and test how some seats fit, especially the infant carriers. That store lets to test fit before buying. Just ask a worker for help.
As for strollers, I don't know what you'll be able to fit that holds 2 infants. I believe you have about 38" in length in the back and many of the tandem strollers are longer when folded. The Graco DuoGlider may work.
=4]This Valco Tri-Mode Twin looks like it would work with the additional car-seat adapter.
I bought a
Baby Jogger City Mini Double last Spring and love it, but it does not work for infant carriers.
Check out
Child Seat Forums for seat info overload. There is also a strollers and gear forum under shopping and deals.