Aww, I'm sorry for your and hubby's loss.
Have to tell you, you'll be on my mind....all day I'm guessing.
I have a ear worm of the Animals song Monterey about Monterey Pop 50 yrs ago
ever since reading your post. You've probably never heard of either

you're too young.
Back to reality - Since it's not the actual anniversary of your MIL's passing couldn't the trip be delayed for several weeks? Even three weeks from now I'm sure you'll be feeling much stronger. Or...convince hubs you'll be okay home alone, or with a visiting friend or family member, while he makes the trip there and back. Should you go, there will most likely be a lot of tending to you on the ride, as well as when you reach your destination. It will be a distraction and increase the time it takes everyone to move at your pace. Add to that the possibility you may be very stiff and sore after the drive, affecting your mood and subsequently hubbies.
I also think in questioning this and bringing it to the forum you know it's probably not the best idea. And since you don't know how it may go, bad or good, why take the chance? If you have a miserable trip there, I suspect the trip back home would only add to your discomfort.
Some have traveled that distance and further once discharged from the hospital but that's normally on heavy narcotics.
@LuvDisney