Purpose: This study assessed mothers' opinions about the feasibility and acceptability of using the ActiGraph GT3X+, Actiheart, and activPAL3 with their 2- to 3-year-old children, as well as with themselves and their husbands/partners, for an 8-day period. Method: Six focus groups were run with Pakistani and White British mothers ("n" = 17), in English or Urdu, at Children's Centers in Bradford, United Kingdom. Each accelerometer was shown to the mothers while its characteristics and wearing procedures were explained. Mothers were then asked about their opinion on the feasibility of use with their toddlers, themselves, and husbands/partners, as well as their monitor preference. Data were transcribed "verbatim" and analyzed through thematic analysis. Results: The ActiGraph was the most preferred accelerometer for use with children, while the Actiheart was the least favorable. The ActiGraph was also the most preferred accelerometer for use with both mothers and fathers. Main issues raised included unsuitability of the Actiheart for fathers due to chest hair, discomfort due to the large size of the activPAL3 in relation to children's thighs, and children pulling off the Actiheart or tampering with the device if its presence was noticed (ActiGraph/Actiheart). Conclusion: The most preferred/accepted accelerometer overall was the ActiGraph GT3X+ for both children and parents. Issues raised with the devices have potential to impact recruitment and compliance rates of studies targeting this population, which highlights the importance of assessing the feasibility/acceptability of different devices with the target population ahead of planning research involving physical activity measurement.