How long will this pollen be around?  Here is the Raleigh timeline.  April is the worst for trees, and next come the grasses:

Spring Allergen Timeline:
Trees: March through June, peaking in April
Grasses: Mid-spring through the fall, peaking May through August
Weeds: August through frost, peaking in September

The pollen is terrible outside!
How to use over-the-counter allergy medicines:
–Mild allergy symptoms, such as sneezing, congestion, and mild eye symptoms, respond well to non-sedating oral antihistamines such as loratadine (Claritin), cetirizine (Zyrtec), Allegra, etc.  Improvement should be noticed within a day or two.  The packages contain dosing instructions for children 2 and …older.
–If red or itchy eyes is the main problem (but your child can still see normally and keeps his/her eyes open), Ketotifen (Zaditor) is a great antihistamine eye drop that is available without a prescription.  Improvement isn’t always immediately noticeable, and if symptoms haven’t improved in 3 days, your child should be evaluated.