A LOT of area schools are on break this week ( if not ALL) and for once we have decent weather predicted in the forecast...so what I am saying is CROWDS!!! MSI will take the whole day ( hopefully they will stay open until 6 vs 5) Shedd will be jammed but doable if you get there early, it is right across form the Field Museum, but honestly, I think each takes a day to really see and get your $ worth...but if you like to skip shows and just view the tanks, the Shedd can be a 1/2 day.I would pack lunch and save some $, not only is the food expensive at each, it gets very crowded and uses up valuable time. I know with traveling that may not be convenient, but even peanut butter sandwiches/ granola bars/chips to tie you over and then get a nice dinner after the places close.
The ledge in the Sears is pretty cool, I have to say,,we waited inthe 2.5 hour lie last summer and while that was painful, it was so cool once we were on the ledges....you can stay up there as long as you like once you do get up. If I were you, I would pay the 50% increase to take the "fastpass" route and head on up...since there are only 2 of you it isn't that bad, we had 6 of us so that was going to break the bank for sure! With the weather predicted, you should have a great view!

One question tho, since we are goint ot have nice weather, maybe don't spend each day indoors at museums? This is RARE for Chicago to have these temps so early, lol, I'm telling you, the poeple will be out! Have a great visit!