There are so many issues with this user but let's focus on the pressing issue. This user seems to want an easy way to track and manage clients/projects for the purpose of sustaining a business.
I would avoid the most of the office suite for this user since there are so many features that it is easy to get lost. I would highly recommend http://www.freshbooks.com/ to the user. This is a one stop shop for invoicing and project tracking. This would handle most of the money related issues that this user would need to tackle. A big advantage is that since this is a subscription service, you get phone support from Freshbooks experts to handle any problems with the software.
Now for contact management, you basically need way to log client interactions. I was poking around and I ran across http://highrisehq.com/ . This is just what what you are looking for. It has a nice interface that allows you to log interactions and setup a to-do list. This has a free version for single users (250 clients or less) and the starting plan is $24 a month (5,000 contacts).
When dealing with user input, the voice/keyboard debate has raged since we started having voice dictation software. While voice control is an option, it can often be more trouble that it is worth. Dragon Naturally Speaking is a good product but it isn't perfect. I would sit down with your user and figure out what deficiencies he has. If he can't type, get him a training course for typing. If he doesn't know English, recommend English classes at the local community college. Sometimes, you have to invest in yourself to be successful.
As for the tablet/laptop debate, it's all about interface. If you feel that he has problems with mouse control and a touch interface is better, then by all means go with a tablet. he is still going to have to know how to type though. Handwriting recognition on tablets are spotty at best. You have to train yourself how to write in a way the tablet can read. This can be really frustrating to many users.
Hope this helps