I'm looking into double strollers. At first I will put Lexi in the seat and snap in LO in the infant carrier. Around the time Lexi is two, I'll ditch the infant seat - will she be too young for the stand and ride option? I'm leaning towards yes, but would love feedback.

BFP #1 mm/c at 12w1d
Re: Stand and Ride Strollers
https://www.target.com/p/graco-ready2grow-classic-connect-trade-stand-ride-stroller-viceroy/-/A-13773930?ref=tgt_adv_XSG10001&AFID=Google_PLA_df&LNM=|13773930&CPNG=Baby&kpid=13773930&LID=PA&ci_src=17588969&ci_sku=13773930&gclid=CPLkvPSBnbwCFQtgMgodSGcAsw
My DD1 and DD2 are 15.5 months apart. We have the Graco Ready to Grow and so far we LOVE it. It has many ways to ride. I like that I can keep my LO right in front of me for now and DD1 still likes riding in the front and watching everything. As they get older it has a little seat with a buckle or a standing option. There are so many ways to ride on it! I just love it.
For me it is easy to open and close. I find for the way I have resolved the logistics of 2 u 2 it is a better fit than the other options. The under storage is massive - which I love. I can get it in and out of the back of my Honda CRV without too much fuss. (I suggest going to Buy Buy Baby or Babies R Us and putting it into and out of your car a few times.) Keep in mind all 2 child strollers will be heavy and more cumbersome, but after messing around with all of them in store, this one made the most sense for us.
We will be taking it to Kauai next week, and I will let you know how it does in all-terrain situations.
We bought ours at Buy Buy Baby after we got them to price match Target ($189) and give us a 25% off coupon we had.
My only criticism? The cup holders are not terribly wide for a sippy cup... so I went and bought some narrower sippy cups. Sometimes it feels long, but I am able to negotiate store and aisles with relative ease compared to some of the other options.
I also have a Joovy caboose. It will take the infant seat and has the "jump seat" (sit/stand seat) for DS1. I love that for shopping. It's very small and easy to maneuver. He does really well with the sit/stand part. I'm surprised.
And then I have a graco tandem that is a BEAST and I really hate it. I bought it used thankfully. Because i am reselling it on Craigslist as we speak!
my friend has the one Bella was talking about and LOVES hers. (Plus my friends kids are a little closer in age than mine.) I like all the different options on it, but I wanted something smaller (I drive a smaller car).
Good luck!
BFP #1 mm/c at 12w1d
I literally gush over this stroller when I talk to people about it. And both girls like riding in both places. I love it so much.
BFP #1 mm/c at 12w1d
Here is the weight capacity from the actual graco website: Front stroller seat holds child up to 50 lbs./rear stroller seat holds child up to 40 lbs./ toddler bench seat & standing platform hold child up to 50lbs. (I have found going to the manufacture's website is more informative on specifics than other retail sites.) The weight capacity is of the child and what the seats can bear. The structure itself can handle in the 90-100 lbs range.
Hopefully this can speak to some specifics? I couldn't find info about the keyfit. It is likely graco can't recommend usage with other seats for liability issues. (That's pretty standard for the "connect/click" type strollers. https://www.gracobaby.com/products/pages/ready2grow-classic-connect-lx-stroller-metropolis.aspx
Good luck! We love ours! Remember BBB will price match and take other people's coupons! Yay!
ETA we didn't use our infant carrier with DD2 for more than about 2 weeks - most of which we were home. IF I ever managed to convince DH to have a 3rd, there would be no infant carseat / carrier in my life. It would be babywear and stroller. Just try chasing after a toddler with an infant car seat. I think the reason I love this stroller so much is because it really gave me a lot of independence for outings without DH. I could bring everything I needed, both babies were secure and safe, and there was no chance of DD1 taking off. She loves to walk, but she is still very little and can only walk for so long. I initially thought a sit and stand was a waste of money, but DD1 loves this thing. She doesn't complain at all about sitting in it, eating snacks, etc. It has been awesome for the zoo, play parks, the mall, etc. I feel like I get out of the house 10x more since I bought this thing. That keeps me sane.