Hi Debbie, You can purchase your tickets on the Disney website by clicking
HERE. If you purchase the Magic My Way ticket and add on the Park Hopper Option, you can visit as many parks in a day as you would like! Without adding the park hopper option, you must choose only 1 park per day.
Since you mentioned you have limited time, I checked on the shipping options. You can do standard shipping (7 - 14 days delivery time), express shipping (up to 7 days delivery time), or you can put your tickets at Will Call. Tickets purchased using Will Call are available at any Theme Park Ticket Sales Location one day after you purchase your tickets on-line. The Will Call option is nice, you won't have to panic that your tickets will arrive on time, and there is no charge to do Will Call.
I hope you and your husband have a wonderful vacation!