April weather is a gamble. I have golfed in April - rare but it has it 80 degrees in April. I have shoveled snow in April as well.
End if April is a better weather risk, but no given. 13 out of the past 15 years we have golfed on May 1st, but the other two we were snowed out.
Valleyfair - the amusement park, will not be open yet in April, opens sometime in mid-late May.
I go to the Mall fairly frequently, whenever we have visitors, in the winter for something to do... etc. Our son loves it, loves Camp Snoopy, but personally, I wouldn't fly here just to go to the Mall. JMHO of course.
I highly recommend MN in the summertime, you can visit the Mall and lot's of outdoor activities. We do have over 14,000 Lakes don't ya know
The MN Zoo is nice, not all that far from the Mall.