We have used the AllRight parking lot the is located on Howell Ave. We have used it 4 times and their shuttle seems very efficient and the drivers nice. Their price is $7/day, but I have always been to find coupons in the Val Pack circulars that come in the mail. It brings it down to $5/day.
As for hotels there are many located also on Howell Ave. I would venture that some even offer airport shuttles.
I grabbed my phone book
The following are all around the 5200 block os South Howell AVe.
Super 8 Motel has free 24 hour airport shuttle and "park and fly package availible"
Clarion also has free 24 hour airport shuttle .
Econolodge has shuttle but doesn't say free. It is on South 13th Street
Howard Johnson saysthey have a "park and fly package"- it is located on 1717 W. Layton.
These offer free airport shuttles:
Holiday Inn -Milwaukee Airport_ West Layton Ave.
Hospitality Inn- 27th and I-894
Well that is all I could find. Hope this helps.