With all the wet weather you may have parts of fields where stand loss is significant. Alot of factors such as extent of stand loss, seed and fuel costs, crop insurance, herbicides planned/used, etc go into a decision to replant. The first decision is can you drive the planter down through the field and replant skips or waterlogged area that have dried. If the field sustained more substantial loss, then doing a stand count is essential. With corn, if you have 70% or more of the initial targeted population (as an example 20,000 out of 28,000 hoped for) remaining and plants are fairly evenly spaced, its probably not economical to tear up the field and replant. With soybeans, if you have 4 plants/ft of row in 30" rows or 1 plant/ft of row in drilled beans that are reasonably spaced there is probably no benefit to replanting, especially if it remains wet and you cant get in the fields for a week or more. If you do replant, you can stick with your intended variety/hybrid maturities unless you have some really long season ones which you likely should avoid, especially with corn after June1.
The above are very general statements. You can find alot more detailed and useful information from an Iowa State publication.