Is your road association set up as a "statutory" road association under 23 MRS 3101-3106, or is it set up as a non-profit? If it's a non-profit, I would guess your bylaws would have to specify what the dues can be used for. But if it's a statutory road association, expenditures are controlled by 23 MRS 3101, subsection 5, which says,
"By a majority vote of the owners present and voting in person or by written proxy or absentee ballot, the owners may determine what repairs and maintenance are necessary and the materials to be furnished or amount of money to be paid by each owner for repairs and maintenance and may determine the amount of money to be paid by each owner for other costs, including, but not limited to, the cost of liability insurance for the officers, directors and owners and costs of administration."
You can read the full test of the law here: https://legislature.maine.gov/legis/statutes/23/title23sec3101.html and if you click on the arrow at the top right hand corner of that page you can scroll through section 3102 - 3106. (Section 3101 subsection 1B defines what is included in "repairs and maintenance.")
I would think that an attorney might be considered a "cost of administration," but I don't see where a picnic table would fit in. My recommendation would be to have a separate fund which people can contribute to on a voluntary basis, if they want to help with the purchase of non-road association items such as a picnic table.
I'd be interested to hear how other road associations have handled this.