In a flurry of local corporate acquisition activity yesterday, Penn Central Corp. announced plans to buy Fair Lanes Inc., a big Baltimore-based bowling center operator.

In addition, a New York investment firm agreed to buy MCD Holdings Inc.; a Baltimore holding company said it will acquire First National Bank in St. Mary's and a local General Electric Co. unit announced plans to buy a Massachusetts computer services firm.

Penn Central, the reorganized successor to the old rail firm that went bankrupt in 1970 and subsequently sold most rail assets for a new regional railroad, Consolidated Rail Corp., said Fair Lanes would be merged into its GSC Six Flags Corp., which operates amusement parks. Fair Lanes owners would receive either $10.50 in cash for each share or $3.50 in cash plus a 5-year, 8 percent installment note. The proposed deal, subject to a final agreement, would be worth about $51 million if all stockholders picked the all-cash offer.

MCD, a Seabrook-based community developer in the Washington and Baltimore markets and owner of the Dahia Mar Yachting Center in Ft. Lauderdale, Fla., will sell substantially all of its assets to a new firm being organized by Oppenheimer and Co. Inc.

A spokesman for MCD said the new Oppenheimer company will assume the MCD name and continue its current operations, with the current management. The proposed purchase will be for cash, with the value tied to the book value of MCD assets on Sept. 30, the end of the Maryland firm's fiscal year.

As of March 31, MCD's assets were listed at nearly $16 million. After the sale, according to the agreement in principle reached yesterday, each MCD stockholders will be allowed to tender shares for cash equal to the book value divided by the number of shares outstanding.

There are 4.24 million shares now out, for a per share value of $3.75. After MCD announced earlier this week that talks on a possible takeover had been started, MCD's stock jumped sharply in heavy over-the-counter trading to $3.50 a share from under $2 a share.

MCD said it will invest all remaining cash ina port-folio of tax exempt municipal bonds, and will register with the Securities and Exchange Commission as an investment company. Proxy material will be sent to stockholders about 30 days after release of financial data for the Sept. 30 final year. The transaction must be approved by stockholders and an independent investment firm will be hired to determine the "fairness" of the proposal to minority owners.

In other acqusition developments:

Mercantile Bankshares Corp. of Baltimore announced an agreement with directors of First National in St. Mary's for a $6 million stock takeover. Mercantile will offer 5 1/4 shares of holding company common for each of 99,918 shares of First National. The plan requires approval by regulatory agencies and acceptance by 80 percent of First National owners.

Mitrol Inc. of Lexington, Mass., will become a subsidiary of General Electric Information Services Co. in Rockville, as of Aug. 31. Mitrol is engaged in custom computer based management and control systems for manufacturing industries, with worldwide sales projected to top $4.5 million by the end of fiscal 1979. Financial details of the GE purchase were not revealed.