Yes, Definitely you can migrate from SQL Server 2008 R2 to SQL Server 2014.
There are two basic strategies for upgrading to a new SQL Server.
1) Full backup with Clean install
2) In-Place Upgrade
As per Michael Otey article. The In-Place Upgrade is Much faster than Full Backup with Clean Install.
If you shall go for "In-Place upgrade" then for all installations of SQL Server, the default compatibility level is set to the version of the Database Engine . As per MSDN BOL Article
Either option 1 or option 2 the SQL server always allow to change compatibality level (in your case SQL Server 2008 R2 to SQL Server 2014).
But you have to keep in mind to migrate any SQL Server . Before doing migration of sql server keep at least you have take Full Backup with full recovery model with native SQL Backup. It's always safeguard in case of production Server.
In your case Compatibility is not issue , Always think about to migration of Old DB engine to new One. If you have past vendor of DB implemention. Always consult with them.