I'd ignore the packaging and plant them whenever you have time. I've never waited until April to plant anything like strawberries, garlic, potatoes, ferns or hostas. Our ground is plenty warm now and the changing air temperatures won't cause it to cool off significantly.

The recommended time to plant garlic is in the fall as it needs a period of cold weather to make it produce cloves. Planting it this late, you'll still get garlic bulbs, but they may not break up into cloves. The garlic you get still will be usable. The recommended time to plant onions and potatoes in OK is February 15 - March 10, with the earliest date being for folks in far SE OK, which warms up first most years, and the latest date being for folks in far NW OK, which warms up last most years. All the rest of us pick a date somewhere in between, depending on where we live in the state and on what the weather is doing.

Any other plants planted from bulbs or roots can go into the ground now as long as the ground isn't sopping wet.

Without knowing what seeds you've started indoors, it is hard to tell you what to do with them next. In general, though, since seedlings started indoors are not exposed to outdoor sunlight (indoor lighting is much, much, much weaker) and outdoor wind must be slowly conditioned to ever-increasing increments of light and wind before they can be permanently moved outdoors. This process is called hardening off, and it is best if performed over a 1 to 2 week period. I harden off plants raised indoors by giving them 1 hour outdoors on their first day, 2 hours the second day, 3 hours the third day, etc. If at any point they show sun or wind damage, I stop the process and hold them indoors to heal, then start over again with 1 hour the first day, 2 the second, etc. If you just abruptly move indoor seedlings outdoors without hardening them off, they'll die. Some people will move them outdoors to full shade during the first week and harden them off in the shade daily, then spend the next week hardening them off in the sun. That works too. We often are hardening off plants in March when the wind blows like mad and, if that is the case, wind burn can kill plants quickly, so it is best to harden them off in a sheltered location on days when the wind is blowing hard.