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n effort by Mayor Martin J. Walsh to enliven City Hall Plaza, the underused civic space at the center of Boston’s downtown, is turning out to be less ambitious than originally envisioned, after the company selected for the job said it ran into logistical and financial obstacles.

Boston Garden Development Corp., a subsidiary of Delaware North Cos., which owns and operates TD Garden, finalized a three-year contract with the city this week to manage seasonal amenities, events, and programs on the plaza.

The first phase of the plan calls for a beer garden, an ice-skating path, and 40 to 50 holiday market vendor stalls — temporary shacks dubbed “chalets’’ — to be installed on the plaza along Cambridge Street, beginning in late October.

The area would open to the public on the Friday following Thanksgiving and operate until the last week of February, though most of the vendors would close on Dec. 31 as the holiday shopping season winds down, the company said Wednesday.

But two key features of the company’s original bid, which beat out those from two competitors, are now uncertain: an “iconic observation wheel’’ with enclosed, climate-controlled gondolas and a full-service restaurant topped with a large, illuminated “#BOSTON’’ sign intended to become a landmark.

TD Garden’s president, Amy Latimer, said the Ferris wheel is being held up by concerns that tunnels under the plaza could make it structurally unsound. She also said the high upfront cost of an observation wheel would require a longer-term deal than the three-year contract the company has with the city.

Construction of a restaurant is complicated by the lack of electric service, plumbing, and other utilities on the barren plaza, a longstanding problem that has bedeviled previous attempts at improving the area.

As a result, neither is likely to be installed next year, Latimer said. She insisted both the restaurant and observation wheel remain possibilities for the future, however.

“The observation wheel and restaurant were possibilities we were suggesting,’’ Latimer said. “You don’t really get to know what’s there until you form the partnership and you really get into what’s available and what the restrictions are. You don’t know that as you’re going through the [bid] process. [The city] didn’t lay out everything — they wanted people to come with grandiose and good ideas.’’

Latimer added that the company was taking a “staged’’ approach and would build on its first season with new amenities and events.

“In the first year of something new like this, our goal is to make sure we do a few things very well and not try to do too much,’’ she said.

City officials said they shared concerns over the mismatch between Delaware North’s original proposal and what it is now planning. But, they said, the contract was always intended to be a test run to learn what improvements are needed on the plaza, part of a broader planning process dubbed “Rethink City Hall.’’

Officials also defended their selection of the Delaware North subsidiary, saying it had stronger financial backing than other applicants and a track record of managing similar spaces, such as the ice rink at Rockefeller Center in New York City. The company has made a commitment to spend $1 million on plaza infrastructure improvements, they added.

“We wanted someone with ties to the community — a proven commodity that had money, that had demonstrated the financial and logistical capacity to do it for this winter,’’ said Patrick Brophy, Walsh’s head of operations. “This is just the very first step. If things are wildly successful, we will be pushing [Delaware North] out of their comfort zone to do something that a little more closely resembles’’ the original proposal.

The Walsh administration’s original effort to liven up the plaza with a season-long winter festival in 2014 came under scrutiny from federal authorities investigating whether city officials had pressured contractors to hire union labor. Walsh officials earlier this year said the first winter festival effort collapsed after they couldn’t come to terms on a lease with its proponent, Anthem Group. That company was also a bidder for the more recent contract won by the Delaware North subsidiary.

Meanwhile, a group involved in the plaza planning praised Walsh for asking residents to help imagine a better plaza, which has been the subject of abortive reinvention efforts going back decades, and said Delaware North’s plans represent a certain amount of progress. But the Boston Preservation Alliance said the temporary buildings planned for this winter don’t mesh with their surroundings, and the group questioned how the Delaware North activities fit in with the broader plan for City Hall.

“We are disappointed that these announced efforts are disconnected and not coordinated with larger, ongoing master-planning efforts for City Hall and the Plaza by a skilled and thoughtful consulting team that recognizes the architectural importance of the building,’’ said Greg Galer, the alliance’s executive director. “They seem to largely ignore the unique design of this place.’’

Under its contract, the Delaware North company will pay all upfront costs to install the improvements, seeking out sponsors and advertisers to help defray the expense. The company will either pay the city a flat fee of $50,000 a year, or a cut based on its financial performance, whichever is greater.

Delaware North said it expects to sell about 50,000 tickets to the ice path, which would also be rented out for youth hockey games and corporate events. Admission and rental fees have not yet been set, the company said. Delaware North expects the small shops to be a mix of Boston-area and national companies, including things like restaurants, retailers, and makers of artisan jewelry.

Based in Buffalo and chaired by Boston Bruins owner Jeremy Jacobs, Delaware North is a longtime operator of sports venues, parks, casinos, concessions, resorts, and restaurants, among other ventures.

Dan Adams can be reached at daniel.adams@globe.com. Follow him on Twitter @Dan_Adams86.