Millions of non-needy children may have to pay a few cents more each day for school lunches under legislation proposed by the Carter administration in its fiscal 1979 budget.

At the same time, the president is proposing a drastic curtailment of outlays for special school milk programs, on grounds that the children who really need the milk are already getting it in the lunches.

These are two kkey features of the president's $9.3 billion spending request for food programs.

Attempts to take aid away from the less needy while enlarging aid for the poor have generated many recent political struggles. Examples: efforts to block tax credits for college tuition, to retain outside-earnings limits on Social Security, to tighten income-cutoff levels for food stamps. A reduction in government purchases of milk is certain to be resisted by the dairy industry.

Two other major changes in food programs are proposed. One would make the school breakfast mandatory in school's with high proportions of poor children. The other would broaden the food-supplement program for low-income pregnant and nursing women and their babies. The cuts in subsidies for lunches and milk would help pay for these increases.

By far the biggest food program is food stamps. Here the budget projects outlays of $5.75 billion and 18 million recipients, a slight increase in each category, but no major changes.

The national school lunch program, which serves 4 billion meals to 25 million youngsters, accounts for two-thirds of the projected $2.7 billion outlay for child nutrition in fiscal 1979.

Children whose families' incomes range up to $7,000 a year for a family of four (about 10 million children) are charged nothing for a lunch. Those in the range of $7,000 to $12,600 for a family of four (about 1.3 million) may be charged no more than 20 cents. Those above $12,600 (13.3 million) pay about 50 cents.

The actual cost of each meal is about $1.06, and the federal share ranges from 27.25 cents for a higher-income child to 92.25 cents for those in the under-$7,000 group.

Under the administration plan, the 27.25-cent subsidy for the child in the higher-income group would be frozen. instead of rising with the cost of living. The other subsidies would continue to rise. Officials said the extra costs to students in the higher-income group would be about 2 cents a meal.

Similar changes are proposed in reimbursement formulas for school breakfasts, which feed about 2.7 million children, mostly low-income. Out-right elimination of subsidies is sought for the high-income group in the child-care program, which feeds about 520,000 children (mostly low-income) in day-care centers. Total savings would shave $105 million from the projected $2.7 million figure.

Official's said another $112 million a year could be saved by eliminating the free-and-low-rate special school milk program (now serving 14 million children) except in schools where there is no lunch program. This would leave about 5.5 million reciptents, officials said. The children in lunch programs are already getting milk, the budget said.