Paediatric training can be intense - usually shift based and lasting 7 years or more, regular nights etc. but it can be rewarding. Training can be part time (although that might make it 14 years). However, once training is completed, many consultant posts are 10 PA and involve a night on call meaning you work about 3 days and one night a week plus the occasional weekend.
Community paediatrics is often less intense although you do need to do basic training first.
You need to compare this to 10 sessions a week as a GP with early starts and evening surgeries, home visits etc. (Although, of course, many GPs simply do sessional work as they choose).
GPwER (previously GPwSI) are being developed but, apart from dermatology, there is no specific requirement. (see response to question below for links).
As a GP with interest in paediatrics you might end up doing child surveillance but could perhaps do more. For this to work and to maintain your skills, you would probably need to do