Children under 8 years, you should not worry much regarding syllabus compatibility.
Every school or board, in general has their own or customized syllabus until 3rd Std.
Its not difficult to make the child adjusted to new school and syllabus. Parental guidnace is a must initially.
To select CBSE, ICSE, IB or State Board is your choice, purely depends on the place you are moving to.
Parents must look at the school’s academic and non-academic excellence over the board choice.
If you find a very good CBSE school nearby, you must give preference to that. Even in some cases, do not hestitate to get admission in a State Board school if its really good. Only problem with state board school might be that some states insists regional laungauge as mandatory, which your child may find it difficult to manage. Also many state government schools do not create good environment for english communication, which is a must these days