Understand that the owner(s) are a peer group and have their own dynamic. It's their company, not yours. If they liked following orders, they'd be employees not owners.
1. Identify the group dynamic (is there a 'holdout', and 'alpha geek')?
2. Identify the objections to your proposed solution.
3. Ask them what their ideal solution(s) would be for this problem.
4. Customize and provide a solution to them.
* rely on the owners having a conversation amongst themselves. If you want to meet with them, meet with all of them at once.
* rely on the owners to convince each other. They may be reluctant to engage each other.
* just talk to people that agree with you. If you do, you're certainly missing the core argument that will shoot down your idea behind closed doors.
You'll probably have to buy new gear and set it up. Desktops can be great. Most people don't like to take work home and lug laptops around anyway.